CVE-2026-102266
High
Description
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.
SeverityHigh
CVSS7.4
Exploit probability—
ProductPyjwt
PublishedSep 28, 2026
First seenSep 28, 2026
Weakness typeCWE-347CWE-347
How to fix
Update
- pyjwt2.14.0 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| pyjwt_project pyjwt | 2.13.0 | — |
| pyjwtPyPI | 2.13.0 ≤ v < 2.14.0 | 2.14.0 |
Check your version
Choose the product and enter the version you run to see whether it falls in the affected range.
In the Intelligence 360 plan
Attack Surface Management
See the assets tied to your domains, the technologies they run and known vulnerabilities in one list.