CVE-2026-102266CWE-347

CVE-2026-102266

High · published September 29, 2026

CVSS v3.1
7.4
EPSS
0%
Percentile
7.4
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
7.4 · HIGH
Vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
CVSS v4.0
Not supplied
EPSS
0.00182 · 7.4th percentile
Weakness
CWE-347 · Improper Verification of Cryptographic Signature
Published
2026-09-29T01:17Z
Affected products (1)
ProductVersionsFixed in
pyjwt_project/pyjwtall versions—
References (4)
https://github.com/jpadilla/pyjwt/commit/f91ed44dd65baaf457f4b3353ed35e98a753934c · [email protected]https://github.com/jpadilla/pyjwt/releases/tag/2.14.0 · [email protected]https://github.com/jpadilla/pyjwt/security/advisories/GHSA-9j54-fg26-wv3r · [email protected]https://github.com/jpadilla/pyjwt/security/advisories/GHSA-9j54-fg26-wv3r · 134c704f-9b21-4f2e-91b3-4a467353bcc0
EPSS history
Timeline
  • 30 SEP 03:24Z
    EPSS moved — → 0%
    epss
  • 28 SEP 20:21Z
    PyJWK accepts empty HMAC keys, bypassing PyJWT's empty-key validation
    cvelistv5