{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "extracted_events": [
              {
                "introduced": "2.13.0"
              },
              {
                "fixed": "2.14.0"
              }
            ],
            "source": [
              "AFFECTED_FIELD",
              "REFERENCES"
            ]
          },
          "events": [
            {
              "introduced": "7144e4534c34810f4525dc4578a32addd8212cff"
            },
            {
              "fixed": "f91ed44dd65baaf457f4b3353ed35e98a753934c"
            },
            {
              "fixed": "c6fe464b356ff4b1ebc9ba62172d331a40aa27df"
            }
          ],
          "repo": "https://github.com/jpadilla/pyjwt",
          "type": "GIT"
        }
      ]
    }
  ],
  "aliases": [
    "GHSA-9j54-fg26-wv3r"
  ],
  "database_specific": {
    "cna_assigner": "GitHub_M",
    "cwe_ids": [
      "CWE-347"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/102xxx/CVE-2026-102266.json"
  },
  "details": "PyJWT is a Python implementation of JSON Web Token standards. From 2.13.0 until 2.14.0, HMACAlgorithm.from_jwk is affected because PyJWK verification path used the decoded key without applying prepare_key validation. This occurs when a trusted JWK Set contains an oct entry with an empty k value. As a result, an attacker signs an HMAC token with the same zero-length key accepted by PyJWT. Consequently, forged token can carry arbitrary authenticated claims. This issue is fixed in version 2.14.0.",
  "id": "CVE-2026-102266",
  "modified": "2026-10-01T03:31:08.614646013Z",
  "published": "2026-09-28T20:21:26.164Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/jpadilla/pyjwt/releases/tag/2.14.0"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/102xxx/CVE-2026-102266.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/jpadilla/pyjwt/security/advisories/GHSA-9j54-fg26-wv3r"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-102266"
    },
    {
      "type": "FIX",
      "url": "https://github.com/jpadilla/pyjwt/commit/f91ed44dd65baaf457f4b3353ed35e98a753934c"
    }
  ],
  "schema_version": "1.9.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "PyJWK accepts empty HMAC keys, bypassing PyJWT's empty-key validation"
}