CVE-2026-102266: Pyjwt Project Pyjwt

Critical severity, CVSS 9.1. EPSS: 0.2% chance of exploitation in the next 30 days.

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

Published 2026-09-28. Last modified 2026-10-07.