CVE-2026-35042

Name: CVE-2026-35042
Creator: NVD / NIST
Published: 2026-04-06T17:17:13.41+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 7.5/10EPSS 0.15%

Last modified Jun 17, 2026

CVE-2026-35042 is a high-severity vulnerability rated 7.5/10 on the CVSS scale. 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. EPSS estimates a 0.15% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1

7.5/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

EPSS Probability

0.15%

5.0th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Nearform	Fast-Jwt	< 6.2.0

References

https://github.com/nearform/fast-jwt/security/advisories/GHSA-hm7r-c7qw-ghp6Exploit, Mitigation, Vendor Advisory
https://www.rfc-editor.org/rfc/rfc7515.html#section-4.1.11Technical Description
https://github.com/nearform/fast-jwt/security/advisories/GHSA-hm7r-c7qw-ghp6Exploit, Mitigation, Vendor Advisory

Timeline

Published: Apr 6, 2026
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2026-35042?

How severe is CVE-2026-35042?

CVE-2026-35042 has a CVSS score of 7.5/10 (HIGH severity). The EPSS model estimates a 0.15% probability of exploitation in the next 30 days.

How do I fix CVE-2026-35042?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2026-35042?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST