CVE-2026-35040

MEDIUM EPSS 30.1%
Published Apr 9, 20262mo ago · Modified Jun 17, 20262w ago
5.3 CVSS 3.1
Medium
Find Similar
Published Apr 9, 2026 2mo ago
Last Modified Jun 17, 2026 2w ago

Description

fast-jwt provides fast JSON Web Token (JWT) implementation. Prior to 6.2.1, using certain modifiers on RegExp objects in the allowedAud, allowedIss, allowedSub, allowedJti, or allowedNonce options in verify functions can cause certain unintended behaviours. This is because some modifiers are stateful and will cause failures in every second verification attempt regardless of the validity of the token provided. Such modifiers are /g (global matching) and /y (sticky matching). This does NOT allow invalid tokens to be accepted, only for valid tokens to be improperly rejected in some configurations. Instead it causes 50% of valid authentication requests to fail in an alternating pattern. This vulnerability is fixed in 6.2.1.

CVSS Details

Base Score
5.3
Exploitability
3.9
Impact
1.4
Vector string
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Attack Vector Network
Attack Complexity Low
Privileges Required None
User Interaction None
Scope Unchanged
Confidentiality None
Integrity None
Availability Low

Threat Intelligence

EPSS Exploit Probability
30.1% percentile
Exploit & Patch Status
Public Exploit Known
Patch Available

Weaknesses 2

CWE-440
CWE-697

Affected Products 1

VendorProductVersionRange
nearformfast-jwt* <6.2.1

References 4

  • github.com https://github.com/nearform/fast-jwt/commit/18d25904e4617e8753526d1b3ab5a2cccdea726a
    Patch
  • github.com https://github.com/nearform/fast-jwt/pull/593
    Issue TrackingPatch
  • github.com https://github.com/nearform/fast-jwt/releases/tag/v6.2.1
    ProductRelease Notes
  • github.com https://github.com/nearform/fast-jwt/security/advisories/GHSA-3j8v-cgw4-2g6q
    ExploitMitigationVendor Advisory

Remediation

  • github.com https://github.com/nearform/fast-jwt/commit/18d25904e4617e8753526d1b3ab5a2cccdea726a
    Patch
  • github.com https://github.com/nearform/fast-jwt/pull/593
    Issue TrackingPatch