CVE-2026-102271
High
Description
PyJWT is a Python implementation of JSON Web Token standards. From 2.4.0 until 2.14.0, PyJWT HMACAlgorithm.prepare_key is affected because asymmetric-key guard relies on textual markers that are absent from DER encoding. This occurs when an application mixes HMAC and asymmetric algorithms and supplies a DER public key as the shared verification key. As a result, PyJWT uses public DER bytes as an HMAC secret. Consequently, an attacker who knows the public key can forge authenticated HMAC tokens. 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
- pyjwt_project pyjwt2.14.0 or later
- pyjwt2.14.0 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| pyjwt_project pyjwt | 2.4.0 ≤ v < 2.14.0 | 2.14.0 |
| pyjwtPyPI | 2.4.0 ≤ v < 2.14.0 | 2.14.0 |
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