jpadilla PyJWT up to 2.13.x PEM Format Recognition jwt/utils.py is_pem_format improper authentication

Summaryinfo

A vulnerability was found in jpadilla PyJWT up to 2.13.x. It has been classified as critical. Impacted is the function is_pem_format of the file jwt/utils.py of the component PEM Format Recognition. The manipulation leads to improper authentication. This vulnerability is referenced as CVE-2026-102268. Remote exploitation of the attack is possible. No exploit is available. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability, which was classified as critical, has been found in jpadilla PyJWT up to 2.13.x. This issue affects the function is_pem_format of the file jwt/utils.py of the component PEM Format Recognition. The manipulation with an unknown input leads to a improper authentication vulnerability. Using CWE to declare the problem leads to CWE-287. When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

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.

The advisory is shared at github.com. The identification of this vulnerability is CVE-2026-102268 since 09/28/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Technical details are known, but no exploit is available.

Upgrading to version 2.14.0 eliminates this vulnerability.

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

Vendor

• jpadilla

Name

• PyJWT

Version

• 2.0
• 2.1
• 2.2
• 2.3
• 2.4
• 2.5
• 2.6
• 2.7
• 2.8
• 2.9
• 2.10
• 2.11
• 2.12
• 2.13

Website

• Product: https://github.com/jpadilla/pyjwt/

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Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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