CVE-2026-102265

PyJWT: Uncaught RecursionError in jwt.decode() on deeply nested token header

PyJWT is a Python implementation of JSON Web Token standards. From 2.13.0 until 2.14.0, PyJWS._load in jwt/api_jws.py is affected because parser catches ValueError but not RecursionError. This occurs when a deeply nested token header reaches json.loads. As a result, RecursionError escapes the documented PyJWT error hierarchy. Consequently, an unauthenticated malformed token can cause a request-level failure and HTTP 500. This issue is fixed in version 2.14.0.

Affected

jpadilla · pyjwt

CVSS v3.1 GITHUB

5.3 MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

EPSS

0.30% chance of exploitation in the next 30 days, 21st percentile

Published

2026-09-28

Updated

2026-10-01

Proof-of-concept exploits (1)

• advisories/GHSA-8wjv-2p76-3863

Security advisories

• jpadilla/pyjwt/security/advisories/GHSA-8wjv-2p76-3863
• jpadilla/pyjwt/commit/06573692ebcdec8831c3927513b3e87c31fbbb62

References

• CVE Record
• NVD entry