Vulnerability-Lookup

PYSEC-2026-177

Vulnerability from pysec - Published: 2026-05-28 16:16 - Updated: 2026-06-02 10:34

Details

PyJWT is a JSON Web Token implementation in Python. Prior to 2.13.0, PyJWKClient.get_signing_key() forces a fresh HTTP request to the JWKS endpoint for every JWT with an unknown kid value, with no rate limiting. Since kid comes from the unverified token header, an attacker can trigger unlimited outbound requests. The vulnerability surfaces only when a JWKS fetch fails; an attacker can attempt to provoke that with sustained unknown-kid traffic, but the outcome depends on upstream JWKS-endpoint behavior (rate limiting, transient errors) which is beyond the attacker's control. This vulnerability is fixed in 2.13.0.

Severity

3.7 (Low)


                  
                    CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L

Impacted products

Name	purl
pyjwt	pkg:pypi/pyjwt

Aliases

JSON

To clipboard

{
  "affected": [
    {
      "ecosystem_specific": {},
      "package": {
        "ecosystem": "PyPI",
        "name": "pyjwt",
        "purl": "pkg:pypi/pyjwt"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "2.13.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "0.1.1",
        "0.1.2",
        "0.1.3",
        "0.1.4",
        "0.1.5",
        "0.1.6",
        "0.1.7",
        "0.1.8",
        "0.1.9",
        "0.2.0",
        "0.2.1",
        "0.2.3",
        "0.3.0",
        "0.3.1",
        "0.3.2",
        "0.4.0",
        "0.4.1",
        "0.4.2",
        "0.4.3",
        "1.0.0",
        "1.0.1",
        "1.1.0",
        "1.3.0",
        "1.4.0",
        "1.4.1",
        "1.4.2",
        "1.5.0",
        "1.5.1",
        "1.5.2",
        "1.5.3",
        "1.6.0",
        "1.6.1",
        "1.6.3",
        "1.6.4",
        "1.7.0",
        "1.7.1",
        "2.0.0",
        "2.0.0a1",
        "2.0.0a2",
        "2.0.1",
        "2.1.0",
        "2.10.0",
        "2.10.1",
        "2.11.0",
        "2.12.0",
        "2.12.1",
        "2.2.0",
        "2.3.0",
        "2.4.0",
        "2.5.0",
        "2.6.0",
        "2.7.0",
        "2.8.0",
        "2.9.0"
      ]
    }
  ],
  "aliases": [
    "CVE-2026-48524",
    "GHSA-fhv5-28vv-h8m8"
  ],
  "details": "PyJWT is a JSON Web Token implementation in Python. Prior to 2.13.0, PyJWKClient.get_signing_key() forces a fresh HTTP request to the JWKS endpoint for every JWT with an unknown kid value, with no rate limiting. Since kid comes from the unverified token header, an attacker can trigger unlimited outbound requests. The vulnerability surfaces only when a JWKS fetch fails; an attacker can attempt to provoke that with sustained unknown-kid traffic, but the outcome depends on upstream JWKS-endpoint behavior (rate limiting, transient errors) which is beyond the attacker\u0027s control. This vulnerability is fixed in 2.13.0.",
  "id": "PYSEC-2026-177",
  "modified": "2026-06-02T10:34:21.056558Z",
  "published": "2026-05-28T16:16:29.403Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://github.com/jpadilla/pyjwt/security/advisories/GHSA-fhv5-28vv-h8m8"
    }
  ],
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L",
      "type": "CVSS_V3"
    }
  ]
}

CVE-2026-48524 (GCVE-0-2026-48524)

Vulnerability from cvelistv5 – Published: 2026-05-28 15:07 – Updated: 2026-05-28 19:17

Title

PyJWT: PyJWKClient unbounded JWKS endpoint requests via attacker-controlled kid values (DoS)

Summary

Severity

3.7 (Low)


                        
                          CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-05-28 19:16 UTC

CWE

CWE-460 - Improper Cleanup on Thrown Exception
CWE-755 - Improper Handling of Exceptional Conditions

Assigner

GitHub_M mitre root

References

1 reference

URL	Tags
https://github.com/jpadilla/pyjwt/security/adviso…	x_refsource_CONFIRM

Impacted products

1 product

Vendor	Product	Version
jpadilla	pyjwt	Affected: < 2.13.0

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-48524",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-05-28T19:16:33.339327Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-05-28T19:17:11.798Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "pyjwt",
          "vendor": "jpadilla",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 2.13.0"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "PyJWT is a JSON Web Token implementation in Python. Prior to 2.13.0, PyJWKClient.get_signing_key() forces a fresh HTTP request to the JWKS endpoint for every JWT with an unknown kid value, with no rate limiting. Since kid comes from the unverified token header, an attacker can trigger unlimited outbound requests. The vulnerability surfaces only when a JWKS fetch fails; an attacker can attempt to provoke that with sustained unknown-kid traffic, but the outcome depends on upstream JWKS-endpoint behavior (rate limiting, transient errors) which is beyond the attacker\u0027s control. This vulnerability is fixed in 2.13.0."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "HIGH",
            "attackVector": "NETWORK",
            "availabilityImpact": "LOW",
            "baseScore": 3.7,
            "baseSeverity": "LOW",
            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L",
            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-460",
              "description": "CWE-460: Improper Cleanup on Thrown Exception",
              "lang": "en",
              "type": "CWE"
            }
          ]
        },
        {
          "descriptions": [
            {
              "cweId": "CWE-755",
              "description": "CWE-755: Improper Handling of Exceptional Conditions",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-05-28T15:07:35.162Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/jpadilla/pyjwt/security/advisories/GHSA-fhv5-28vv-h8m8",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/jpadilla/pyjwt/security/advisories/GHSA-fhv5-28vv-h8m8"
        }
      ],
      "source": {
        "advisory": "GHSA-fhv5-28vv-h8m8",
        "discovery": "UNKNOWN"
      },
      "title": "PyJWT: PyJWKClient unbounded JWKS endpoint requests via attacker-controlled kid values (DoS)"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-48524",
    "datePublished": "2026-05-28T15:07:35.162Z",
    "dateReserved": "2026-05-21T16:18:10.619Z",
    "dateUpdated": "2026-05-28T19:17:11.798Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

GHSA-FHV5-28VV-H8M8

Vulnerability from github – Published: 2026-06-15 17:28 – Updated: 2026-07-31 22:13

Summary

PyJWKClient unbounded JWKS endpoint requests via attacker-controlled kid values (DoS)

Details

[!NOTE] The vulnerability surfaces only when a JWKS fetch fails; an attacker can attempt to provoke that with sustained unknown-kid traffic, but the outcome depends on upstream JWKS-endpoint behavior (rate limiting, transient errors) which is beyond the attacker's control. Impact is reduced auth availability until the next successful fetch, not complete denial of service.

Summary

PyJWKClient.get_signing_key() forces a fresh HTTP request to the JWKS endpoint for every JWT with an unknown kid value, with no rate limiting. Since kid comes from the unverified token header, an attacker can trigger unlimited outbound requests.

Additionally, fetch_data() finally block clears the JWKS cache on network error.

Root Cause

jwt/jwks_client.py:172-198 - get_signing_key(kid) calls get_signing_keys(refresh=True) for unknown kids, bypassing TTL cache with no cooldown. jwt/jwks_client.py:120-122 - finally block writes None to cache on error, clearing valid data.

Impact

DoS against JWKS endpoint (unlimited requests per invalid token)
DoS against application (network I/O latency)
Cascading failure (rate limiting clears cache, breaking legitimate auth)

Suggested Fix

Add refresh cooldown (refuse refresh more than once per TTL period)
Move cache write from finally to else block

Affected Versions

All versions with PyJWKClient (2.4.0 through 2.12.1)

Severity

3.7 (Low)


                  
                    CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 2.12.1"
      },
      "package": {
        "ecosystem": "PyPI",
        "name": "pyjwt"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.0.0"
            },
            {
              "fixed": "2.13.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-48524"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-460",
      "CWE-755"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-06-15T17:28:46Z",
    "nvd_published_at": "2026-05-28T16:16:29Z",
    "severity": "LOW"
  },
  "details": "\u003e [!NOTE]\n\u003e  The vulnerability surfaces only when a JWKS fetch fails; an attacker can attempt to provoke that with sustained unknown-kid traffic, but the outcome depends on upstream JWKS-endpoint behavior (rate limiting, transient errors) which is beyond the attacker\u0027s control. Impact is reduced auth availability until the next successful fetch, not complete denial of service.\n\n## Summary\nPyJWKClient.get_signing_key() forces a fresh HTTP request to the JWKS endpoint for every JWT with an unknown kid value, with no rate limiting. Since kid comes from the unverified token header, an attacker can trigger unlimited outbound requests.\n\nAdditionally, fetch_data() finally block clears the JWKS cache on network error.\n\n## Root Cause\njwt/jwks_client.py:172-198 - get_signing_key(kid) calls get_signing_keys(refresh=True) for unknown kids, bypassing TTL cache with no cooldown.\njwt/jwks_client.py:120-122 - finally block writes None to cache on error, clearing valid data.\n\n## Impact\n- DoS against JWKS endpoint (unlimited requests per invalid token)\n- DoS against application (network I/O latency)\n- Cascading failure (rate limiting clears cache, breaking legitimate auth)\n\n## Suggested Fix\n1. Add refresh cooldown (refuse refresh more than once per TTL period)\n2. Move cache write from finally to else block\n\n## Affected Versions\nAll versions with PyJWKClient (2.4.0 through 2.12.1)",
  "id": "GHSA-fhv5-28vv-h8m8",
  "modified": "2026-07-31T22:13:02Z",
  "published": "2026-06-15T17:28:46Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/jpadilla/pyjwt/security/advisories/GHSA-fhv5-28vv-h8m8"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-48524"
    },
    {
      "type": "WEB",
      "url": "https://github.com/github/advisory-database/pull/8522"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/jpadilla/pyjwt"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pypa/advisory-database/tree/main/vulns/pyjwt/PYSEC-2026-177.yaml"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L",
      "type": "CVSS_V3"
    }
  ],
  "summary": "PyJWKClient unbounded JWKS endpoint requests via attacker-controlled kid values (DoS)"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.

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PYSEC-2026-177

CVE-2026-48524 (GCVE-0-2026-48524)

GHSA-FHV5-28VV-H8M8

Summary

Root Cause

Impact

Suggested Fix

Affected Versions

Tags

Sightings

Nomenclature

Related by attack behaviour