fast-jwt provides fast JSON Web Token (JWT) implementation. In 6.1.0 and earlier, fast-jwt does not validate the crit (Critical) Header Parameter defined in RFC 7515 §4.1.11. When a JWS token contains a crit array listing extensions that fast-jwt does not understand, the library accepts the token instead of rejecting it. This violates the MUST requirement in the RFC.
History

Tue, 07 Apr 2026 18:00:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Tue, 07 Apr 2026 00:00:00 +0000

Type Values Removed Values Added
First Time appeared Nearform
Nearform fast-jwt
Vendors & Products Nearform
Nearform fast-jwt

Mon, 06 Apr 2026 18:00:00 +0000

Type Values Removed Values Added
Description fast-jwt provides fast JSON Web Token (JWT) implementation. In 6.1.0 and earlier, fast-jwt does not validate the crit (Critical) Header Parameter defined in RFC 7515 §4.1.11. When a JWS token contains a crit array listing extensions that fast-jwt does not understand, the library accepts the token instead of rejecting it. This violates the MUST requirement in the RFC.
Title fast-jwt accepts unknown `crit` header extensions (RFC 7515 §4.1.11 MUST violation)
Weaknesses CWE-345
CWE-636
References
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N'}


cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published: 2026-04-06T17:02:12.180Z

Updated: 2026-04-07T15:59:49.872Z

Reserved: 2026-03-31T21:06:06.428Z

Link: CVE-2026-35042

cve-icon Vulnrichment

Updated: 2026-04-07T15:19:44.996Z

cve-icon NVD

Status : Undergoing Analysis

Published: 2026-04-06T17:17:13.410

Modified: 2026-04-07T17:16:29.590

Link: CVE-2026-35042

cve-icon Redhat

No data.