CVE-2026-102272

High

Description

PyJWT is a Python implementation of JSON Web Token standards. From 2.13.0 until 2.14.0, HMACAlgorithm.prepare_key in jwt/algorithms.py is affected because raw-JWK detector does not normalize accepted Unicode byte-order marks before checking for JSON. This occurs when a public JWK is prefixed with a UTF-8 BOM and used in a mixed-algorithm verification path. As a result, public JWK bypasses asymmetric-key detection and becomes the HMAC secret. Consequently, an attacker who knows the public key can forge authenticated 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

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

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