Vulnerability in Jpadilla Pyjwt
CVE-2026-102266
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.
Published .
CVSS v3 metric
CVSS v3 base score 7.4 (High). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
- Jpadilla Pyjwt — versions >= 2.13.0, < 2.14.0
Weakness classification (CWE)
References
Frequently asked questions
- What is CVE-2026-102266?
- CVE-2026-102266 is a high-severity vulnerability in Jpadilla Pyjwt, classified under Improper Verification of Cryptographic Signature. CVSS score: 7.4/10. Published 2026-09-28.
- How severe is CVE-2026-102266?
- High severity. CVSS v3 base score is 7.4 out of 10.