ubuntu-cve-2026-48523
Vulnerability from osv_ubuntu
Published
2026-05-28 16:16
Modified
2026-06-03 11:26
Summary
Details

PyJWT is a JSON Web Token implementation in Python. From 2.9.0 to 2.12.1, there is a verifier-side algorithm allow-list bypass when jwt.decode() or jwt.decode_complete() are called with a PyJWK key. The token header alg is checked against the caller-supplied algorithms allow-list, but signature verification is performed with the algorithm bound to the PyJWK object instead of the header algorithm. An attacker who controls a registered JWK/JWKS private key can sign with a disallowed algorithm, advertise an allowed algorithm in the JWT header, and still be accepted. The issue affects the documented PyJWKClient.get_signing_key_from_jwt(...) flow. This vulnerability is fixed in 2.13.0.

Severity
5.4 (Medium)
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
N/A (UNKNOWN)
medium
References
To clipboard 

{
  "affected": [
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "python-jwt",
            "binary_version": "1.3.0-1ubuntu0.1+esm1"
          },
          {
            "binary_name": "python3-jwt",
            "binary_version": "1.3.0-1ubuntu0.1+esm1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:16.04:LTS",
        "name": "pyjwt",
        "purl": "pkg:deb/ubuntu/pyjwt@1.3.0-1ubuntu0.1+esm1?arch=source\u0026distro=esm-infra/xenial"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.0.0-0ubuntu1",
        "1.3.0-1",
        "1.3.0-1ubuntu0.1",
        "1.3.0-1ubuntu0.1+esm1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "python-jwt",
            "binary_version": "1.5.3+ds1-1ubuntu0.1+esm1"
          },
          {
            "binary_name": "python3-jwt",
            "binary_version": "1.5.3+ds1-1ubuntu0.1+esm1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:18.04:LTS",
        "name": "pyjwt",
        "purl": "pkg:deb/ubuntu/pyjwt@1.5.3+ds1-1ubuntu0.1+esm1?arch=source\u0026distro=esm-infra/bionic"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.4.2-1.1",
        "1.5.3+ds1-1",
        "1.5.3+ds1-1ubuntu0.1",
        "1.5.3+ds1-1ubuntu0.1+esm1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "python3-jwt",
            "binary_version": "1.7.1-2ubuntu2.1+esm1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:20.04:LTS",
        "name": "pyjwt",
        "purl": "pkg:deb/ubuntu/pyjwt@1.7.1-2ubuntu2.1+esm1?arch=source\u0026distro=esm-infra/focal"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.7.0-2",
        "1.7.1-1",
        "1.7.1-2ubuntu1",
        "1.7.1-2ubuntu2",
        "1.7.1-2ubuntu2.1",
        "1.7.1-2ubuntu2.1+esm1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "python3-jwt",
            "binary_version": "2.3.0-1ubuntu0.3"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:22.04:LTS",
        "name": "pyjwt",
        "purl": "pkg:deb/ubuntu/pyjwt@2.3.0-1ubuntu0.3?arch=source\u0026distro=jammy"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.7.1-2ubuntu2",
        "2.1.0-1",
        "2.3.0-1",
        "2.3.0-1ubuntu0.1",
        "2.3.0-1ubuntu0.2",
        "2.3.0-1ubuntu0.3"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "python3-jwt",
            "binary_version": "2.7.0-1ubuntu0.1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:24.04:LTS",
        "name": "pyjwt",
        "purl": "pkg:deb/ubuntu/pyjwt@2.7.0-1ubuntu0.1?arch=source\u0026distro=noble"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "2.7.0-1",
        "2.7.0-1ubuntu0.1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "python3-jwt",
            "binary_version": "2.10.1-2ubuntu0.1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:25.10",
        "name": "pyjwt",
        "purl": "pkg:deb/ubuntu/pyjwt@2.10.1-2ubuntu0.1?arch=source\u0026distro=questing"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "2.10.1-2",
        "2.10.1-2ubuntu0.1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "python3-jwt",
            "binary_version": "2.10.1-4ubuntu1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:26.04:LTS",
        "name": "pyjwt",
        "purl": "pkg:deb/ubuntu/pyjwt@2.10.1-4ubuntu1?arch=source\u0026distro=resolute"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "2.10.1-2",
        "2.10.1-3",
        "2.10.1-3build1",
        "2.10.1-4",
        "2.10.1-4ubuntu1"
      ]
    }
  ],
  "aliases": [],
  "details": "PyJWT is a JSON Web Token implementation in Python. From 2.9.0 to 2.12.1, there is a verifier-side algorithm allow-list bypass when jwt.decode() or jwt.decode_complete() are called with a PyJWK key. The token header alg is checked against the caller-supplied algorithms allow-list, but signature verification is performed with the algorithm bound to the PyJWK object instead of the header algorithm. An attacker who controls a registered JWK/JWKS private key can sign with a disallowed algorithm, advertise an allowed algorithm in the JWT header, and still be accepted. The issue affects the documented PyJWKClient.get_signing_key_from_jwt(...) flow. This vulnerability is fixed in 2.13.0.",
  "id": "UBUNTU-CVE-2026-48523",
  "modified": "2026-06-03T11:26:16Z",
  "published": "2026-05-28T16:16:00Z",
  "references": [
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2026-48523"
    },
    {
      "type": "REPORT",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-48523"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/jpadilla/pyjwt/security/advisories/GHSA-jq35-7prp-9v3f"
    }
  ],
  "related": [],
  "schema_version": "1.7.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N",
      "type": "CVSS_V3"
    },
    {
      "score": "medium",
      "type": "Ubuntu"
    }
  ],
  "upstream": [
    "CVE-2026-48523"
  ]
}



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