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Vulnerability record · CVE-2026-35042 · published 6 April 2026

CVE-2026-35042: Nearform fast-jwt insufficient verification of data authenticity vulnerability

Nearform · Fast Jwt

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.

7.5 CVSS 3.1 High EPSS 0.20% · top 91.2% CWE-345 · Insufficient verification of data authenticityCWE-636 · CWE-636
7.5CVSS 3.1 base score
0.20%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
3References, 2 tagged exploit
17 Jun 2026Last modified by NVD

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.

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

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/nearform/fast-jwt/security/advisories/GHSA-hm7r-c7qw-ghp6 ExploitMitigationVendor Advisory
https://www.rfc-editor.org/rfc/rfc7515.html#section-4.1.11 Technical Description
https://github.com/nearform/fast-jwt/security/advisories/GHSA-hm7r-c7qw-ghp6 ExploitMitigationVendor Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

9.1CVE-2026-35039Nearform fast-jwt insufficient verification of data authenticity vulnerabilityfast-jwt provides fast JSON Web Token (JWT) implementation. From 0.0.1 to before 6.2.0, setting up a custom cacheKeyBuilder method which does not pro…EPSS 0.22%9.1CVE-2026-34950Nearform fast-jwt broken cryptographic algorithm vulnerabilityfast-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 ^ an…EPSS 0.27%6.5CVE-2026-35041Nearform fast-jwt inefficient regular expression (redos) vulnerabilityfast-jwt provides fast JSON Web Token (JWT) implementation. From 5.0.0 to 6.2.0, a denial-of-service condition exists in fast-jwt when the allowedAud…EPSS 0.43%5.9CVE-2023-48223Nearform fast-jwt improper input validation vulnerabilityfast-jwt provides fast JSON Web Token (JWT) implementation. Prior to version 3.3.2, the fast-jwt library does not properly prevent JWT algorithm conf…EPSS 0.68%5.3CVE-2026-35040Nearform fast-jwt vulnerabilityfast-jwt provides fast JSON Web Token (JWT) implementation. Prior to 6.2.1, using certain modifiers on RegExp objects in the allowedAud, allowedIss, …EPSS 0.63%7.8CVE-2023-38831WinRAR ZIP archive spoofing leads to arbitrary code executionWinRAR before 6.23 mishandles ZIP archives that contain a benign file and a folder with the same name, causing the folder's contents to be processed …KEVEPSS 100%analysed9.8CVE-2022-26871Trend Micro Apex Central unauthenticated arbitrary file uploadTrend Micro Apex Central (and Apex One) contains an arbitrary file upload flaw caused by insufficient verification of data authenticity (CWE-345). An…KEVEPSS 19%analysed

Source: NIST National Vulnerability Database (record CVE-2026-35042), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.