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.
Affected products
pyjwt_project: pyjwt
References4
- github.com/jpadilla/pyjwt/security/advisories/GHSA-p4g4-x82p-q7… ExploitPatchVendor Advisory
- github.com/jpadilla/pyjwt/security/advisories/GHSA-p4g4-x82p-q7… ExploitPatchVendor Advisory
- github.com/jpadilla/pyjwt/commit/2798504fa2663364573cf2d1043d8d… Patch
- github.com/jpadilla/pyjwt/releases/tag/2.14.0 ProductRelease Notes
Metrics
- CVSS 3.1
-
7.4
HIGH
Score source: CNA
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N - EPSS — exploit probability
- 0% percentile: 12 · as of 9 November 2026
- CWE
- CWE-347
Could this be exploited in your environment?
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