{"id":"PYSEC-2026-176","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":["CVE-2026-48523","GHSA-jq35-7prp-9v3f"],"modified":"2026-06-02T12:15:06.164180860Z","published":"2026-05-28T16:16:29.280Z","references":[{"type":"EVIDENCE","url":"https://github.com/jpadilla/pyjwt/security/advisories/GHSA-jq35-7prp-9v3f"}],"affected":[{"package":{"name":"pyjwt","ecosystem":"PyPI","purl":"pkg:pypi/pyjwt"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"2.9.0"},{"fixed":"2.12.1"}]}],"versions":["2.10.0","2.10.1","2.11.0","2.12.0","2.9.0"],"ecosystem_specific":{},"database_specific":{"source":"https://github.com/pypa/advisory-database/blob/main/vulns/pyjwt/PYSEC-2026-176.yaml"}}],"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"}]}