Description
PyJWT is a Python implementation of JSON Web Token standards. From 2.13.0 until 2.14.0, HMACAlgorithm.from_jwk is affected because PyJWK verification path used the decoded key without applying prepare_key validation. This occurs when a trusted JWK Set contains an oct entry with an empty k value. As a result, an attacker signs an HMAC token with the same zero-length key accepted by PyJWT. Consequently, forged token can carry arbitrary authenticated claims. This issue is fixed in version 2.14.0.
Published: 2026-09-28
Score: 7.4 High
EPSS: n/a
KEV: No
Impact: n/a
Action: n/a
AI Analysis

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Remediation

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History

Mon, 28 Sep 2026 20:30:00 +0000

Type Values Removed Values Added
Description PyJWT is a Python implementation of JSON Web Token standards. From 2.13.0 until 2.14.0, HMACAlgorithm.from_jwk is affected because PyJWK verification path used the decoded key without applying prepare_key validation. This occurs when a trusted JWK Set contains an oct entry with an empty k value. As a result, an attacker signs an HMAC token with the same zero-length key accepted by PyJWT. Consequently, forged token can carry arbitrary authenticated claims. This issue is fixed in version 2.14.0.
Title PyJWK accepts empty HMAC keys, bypassing PyJWT's empty-key validation
Weaknesses CWE-347
References
Metrics cvssV3_1

{'score': 7.4, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N'}

Subscriptions

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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-09-28T20:21:26.164Z

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

Link: CVE-2026-102266

cve-icon Vulnrichment

No data.

cve-icon NVD

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cve-icon Redhat

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cve-icon OpenCVE Enrichment

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Weaknesses
  • CWE-347

    Improper Verification of Cryptographic Signature