CVE-2026-102266 (GCVE-0-2026-102266)

Vulnerability from cvelistv5 – Published: 2026-09-28 20:21 – Updated: 2026-09-29 19:35
VLAI
Title
PyJWK accepts empty HMAC keys, bypassing PyJWT's empty-key validation
Summary
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.
Severity
7.4 (High)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
SSVC
Exploitation: poc Automatable: no Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-09-29 19:28 UTC
CWE
  • CWE-347 - Improper Verification of Cryptographic Signature
Assigner
GitHub_M CNA under the mitre root
CNA scorecard C 72/100 over 7994 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
jpadilla pyjwt Affected: >= 2.13.0, < 2.14.0
guessed Create a notification for this product.
Show details on NVD website
To clipboard 

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