{"id":"CVE-2026-48523","summary":"PyJWT: Algorithm allow-list bypass when decoding with `PyJWK` / `PyJWKClient` keys","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.","aliases":["GHSA-jq35-7prp-9v3f","PYSEC-2026-176"],"modified":"2026-06-24T18:29:19.259007989Z","published":"2026-05-28T15:10:19.141Z","related":["CGA-vrmj-m992-2qrx","SUSE-SU-2026:22138-1","SUSE-SU-2026:22170-1","SUSE-SU-2026:22220-1","openSUSE-SU-2026:11024-1"],"database_specific":{"cna_assigner":"GitHub_M","cwe_ids":["CWE-347"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/48xxx/CVE-2026-48523.json"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/48xxx/CVE-2026-48523.json"},{"type":"ADVISORY","url":"https://github.com/jpadilla/pyjwt/security/advisories/GHSA-jq35-7prp-9v3f"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-48523"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/jpadilla/pyjwt","events":[{"introduced":"868cf4ab2ca5a0a39da40e5a14dd740b203662b2"},{"fixed":"7144e4534c34810f4525dc4578a32addd8212cff"}],"database_specific":{"source":["AFFECTED_FIELD","CPE_RANGE"],"cpe":"cpe:2.3:a:pyjwt_project:pyjwt:*:*:*:*:*:*:*:*","extracted_events":[{"introduced":"2.9.0"},{"fixed":"2.13.0"},{"introduced":"2.9.0"},{"fixed":"2.12.1"}]}}],"versions":["2.12.1","2.12.0","2.11.0","2.10.1","2.10.0","2.9.0"],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-48523.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N"}]}