Is CVE-2026-102266 being exploited?

No public exploit is currently tracked.

How severe is CVE-2026-102266?

CVE-2026-102266 has a CVSS v3 severity of HIGH (7.4).

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CVE-2026-102266

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.