CVE-2026-48523

CVE-2026-48523 · PyJWT: Algorithm allow-list bypass when decoding with `PyJWK` / `PyJWKClient` keys

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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.

CVSS 5.4 · Moyenne · EPSS 0,1% · Correctif disponible

Publication

2026-05-28T15:10:19.141Z

Mise à jour

2026-05-28T15:27:49.780Z

Pile logicielle: system · python

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