CVE-2026-102266
PyJWK accepts empty HMAC keys, bypassing PyJWT's empty-key validation
CVSS Score
7.4
EPSS Score
0.0%
EPSS Percentile
0th
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.
| CWE | CWE-347 |
| Vendor | jpadilla |
| Product | pyjwt |
| Published | Sep 28, 2026 |
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CVSS v3 Breakdown
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None
Affected Versions
jpadilla / pyjwt
>= 2.13.0, < 2.14.0