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CVE PROGRAM SOURCE RECORD7.4 High

CVE-2026-102266

PyJWK accepts empty HMAC keys, bypassing PyJWT's empty-key validation

Description

PyJWT is a Python implementation of JSON Web Token standards. From 2.13.0 until 2.14.0, HMACAlgorithm.from_jwk is affected because PyJWK verification path used the decoded key without applying prepare_key validation. This occurs when a trusted JWK Set contains an oct entry with an empty k value. As a result, an attacker signs an HMAC token with the same zero-length key accepted by PyJWT. Consequently, forged token can carry arbitrary authenticated claims. This issue is fixed in version 2.14.0.

Affected products

Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.

jpadilla pyjwt

  • >= 2.13.0, < 2.14.0affected

References