CVE-2026-102268

Critical

Description

PyJWT is a Python implementation of JSON Web Token standards. Prior to 2.14.0, is_pem_format in jwt/utils.py is affected because is_pem_format does not recognize every PEM representation accepted by the cryptography loader. This occurs when an application mixes HMAC and asymmetric algorithms and supplies a mutated public-key PEM as raw key bytes. As a result, HMACAlgorithm.prepare_key treats the unrecognized asymmetric public key 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.

SeverityCritical

CVSS9.1

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	v < 2.14.0	2.14.0
pyjwtPyPI	v < 2.14.0	2.14.0

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