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.
Fix
Patch, vendor advisory and mitigation references on NVD 2
- https://github.com/jpadilla/pyjwt/security/advisories/GHSA-jq35-7prp-9v3f Exploit, Vendor Advisory
- https://github.com/jpadilla/pyjwt/security/advisories/GHSA-jq35-7prp-9v3f Exploit, Vendor Advisory
Every line above is quoted from NVD, CISA, Microsoft, the vendor's own advisory or DISA; nothing is generated.
Change history 1
- First seenCVSS 5.4 · pyjwt_projectNVD modified 2026-10-25 23:10
Affected (CPE criteria) 1
cpe:2.3:a:pyjwt_project:pyjwt:*:*:*:*:*:*:*:*
References 2
- https://github.com/jpadilla/pyjwt/security/advisories/GHSA-jq35-7prp-9v3f Exploit, Vendor Advisory
- https://github.com/jpadilla/pyjwt/security/advisories/GHSA-jq35-7prp-9v3f Exploit, Vendor Advisory