cyfenced.com →

[ CVE-2026-102271 · Published 28 Sep 2026 ]

PyJWT: Public keys in DER form are accepted as HMAC secrets, bypassing the CVE-2022-29217 guard

CVSS 7.4 EPSS <1%2 agency advisoriesFix available

[ Why it matters ]Priority signals

  • Public proof-of-concept exploit exists (CISA SSVC)

[ Description ]Official description

PyJWT is a Python implementation of JSON Web Token standards. From 2.4.0 until 2.14.0, PyJWT HMACAlgorithm.prepare_key is affected because asymmetric-key guard relies on textual markers that are absent from DER encoding. This occurs when an application mixes HMAC and asymmetric algorithms and supplies a DER public key as the shared verification key. As a result, PyJWT uses public DER bytes 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.

[ Fixes ]Fixes and patches

  • pyjwt 2.14.0Fixed version · GitHub Advisories · pip package pyjwt: upgrade to 2.14.0 or later (affected >= 2.4.0, < 2.14.0)
  • Patch on github.comVendor patch or bulletin · NVD · Reference tagged 'Patch' by NVD
  • Patch on github.comVendor patch or bulletin · NVD · Reference tagged 'Patch' by NVD

[ Advisories ]Government CERT advisories

[ Packages ]Affected open-source packages

[ References ]References