CVE-2026-34950

Name: CVE-2026-34950
Creator: NVD / NIST
Published: 2026-04-06T16:16:38.017+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

CRITICALCVSS 9.1/10EPSS 0.24%

Last modified Jun 17, 2026

CVE-2026-34950 is a critical-severity vulnerability rated 9.1/10 on the CVSS scale. fast-jwt provides fast JSON Web Token (JWT) implementation. In 6.1.0 and earlier, the publicKeyPemMatcher regex in fast-jwt/src/crypto.js uses a ^ anchor that is defeated by any leading whitespace in the key string, re-enabling the exact same JWT algorithm confusion attack that CVE-2023-48223 patched.. EPSS estimates a 0.24% chance of exploitation in the next 30 days.

Description

fast-jwt provides fast JSON Web Token (JWT) implementation. In 6.1.0 and earlier, the publicKeyPemMatcher regex in fast-jwt/src/crypto.js uses a ^ anchor that is defeated by any leading whitespace in the key string, re-enabling the exact same JWT algorithm confusion attack that CVE-2023-48223 patched.

Metrics

CVSS 3.1

9.1/10

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

EPSS Probability

0.24%

14.3th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-327

Affected Software

Vendor	Product	Versions
Nearform	Fast-Jwt	< 6.2.0

References

https://github.com/nearform/fast-jwt/security/advisories/GHSA-mvf2-f6gm-w987Exploit, Vendor Advisory

Timeline

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

Frequently Asked Questions

What is CVE-2026-34950?

How severe is CVE-2026-34950?

CVE-2026-34950 has a CVSS score of 9.1/10 (CRITICAL severity). The EPSS model estimates a 0.24% probability of exploitation in the next 30 days.

How do I fix CVE-2026-34950?

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-2026-34950?

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

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Source: NVD / NIST