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.
Published: 2026-09-28
Score: 9.1 Critical
EPSS: n/a
KEV: No
Impact: n/a
Action: n/a
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Remediation

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History

Mon, 28 Sep 2026 20:45:00 +0000

Type Values Removed Values Added
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.
Title PyJWT: Asymmetric-PEM detection bypass: whitespace/line-ending-mutated public keys skip the HS/asymmetric confusion guard
Weaknesses CWE-347
References
Metrics cvssV3_1

{'score': 9.1, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N'}


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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-09-28T20:26:13.674Z

Reserved: 2026-09-28T20:11:16.658Z

Link: CVE-2026-102268

cve-icon Vulnrichment

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cve-icon Redhat

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cve-icon OpenCVE Enrichment

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Weaknesses