CVEvulnerability

CVE-2026-48523

5.4 MEDIUM Published 2026-05-28 Modified 2026-10-25 Official page ↗
Status
Analyzed
Published
2026-05-28
Last modified
2026-10-25
Assigner
[email protected]
CVSS 3.1 ([email protected])
5.4 MEDIUM — CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
Weaknesses
CWE-347

Description

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.

Affected configurations

• pyjwt project pyjwt (>= 2.9.0 < 2.13.0)

Related

Weakness · CWE (1)

  • CWE-347 Improper Verification of Cryptographic Signature weakness

References