CVE-2026-102271
Consequently, an attacker who knows the public key can forge authenticated HMAC tokens.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.21%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
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.
- CVSS 3.1
- 7.4 HIGHCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
- EPSS
- 0.21% probability · 12th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Weakness
- CWE-347
- Affected
- pyjwt project/pyjwt
- Source
- security-advisories@github.com
EPSS moved from 0.2% on 29 September 2026 to 0.2% on 26 October 2026.
References
- https://github.com/jpadilla/pyjwt/commit/2798504fa2663364573cf2d1043d8d7fef389499Patch
- https://github.com/jpadilla/pyjwt/releases/tag/2.14.0Product, Release Notes
- https://github.com/jpadilla/pyjwt/security/advisories/GHSA-p4g4-x82p-q773Exploit, Patch, Vendor Advisory
- https://github.com/jpadilla/pyjwt/security/advisories/GHSA-p4g4-x82p-q773Exploit, Patch, Vendor Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.