high7.4
CVE-2026-102266
PyJWT: PyJWK accepts empty HMAC keys, bypassing PyJWT's empty-key validation
Impact
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.
Affected packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| pip | PyJWT | >= 2.13.0, < 2.14.0 | 2.14.0 |
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| Pyjwt Project | Pyjwt | Version 2.13.0 |
Weakness classification
References
- NVD record
- CVE.org record
- GitHub advisory
- https://github.com/advisories/GHSA-9j54-fg26-wv3r
- https://github.com/jpadilla/pyjwt/security/advisories/GHSA-9j54-fg26-wv3r
- https://nvd.nist.gov/vuln/detail/CVE-2026-102266
- https://github.com/jpadilla/pyjwt/commit/f91ed44dd65baaf457f4b3353ed35e98a753934c
- https://github.com/jpadilla/pyjwt/releases/tag/2.14.0