CVE-2026-102266Published

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

Exact source revision recorded 23 Oct 2026 15:48:27 UTC. It does not establish the source's current position. Latest evidence.

Recorded JSON

cve-program · CVE-2026-102266

Published

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.

Source published: 28 Sep 2026 20:21:26 UTC
Source modified: 29 Sep 2026 19:35:42 UTC
Observed here: 23 Oct 2026 15:48:27 UTC
Source terms: CVE Program Terms of Use

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CVSS 3.1 · 7.4 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N