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CVE-2026-35040 Details

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.

Metrics

CVSS 3.x Severity and Vector Strings:

CNA: [email protected]CVSS-B:5.3 MEDIUMVector:CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

References to Advisories, Solutions, and Tools

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URL	Source(s)	Tag(s)
https://github.com/nearform/fast-jwt/commit/18d25904e4617e8753526d1b3ab5a2cccdea726a	[email protected]	Patch
https://github.com/nearform/fast-jwt/pull/593	[email protected]	Issue TrackingPatch
https://github.com/nearform/fast-jwt/releases/tag/v6.2.1	[email protected]	ProductRelease Notes
https://github.com/nearform/fast-jwt/security/advisories/GHSA-3j8v-cgw4-2g6q	[email protected]	ExploitMitigationVendor Advisory

Weakness Enumeration

CWE-ID	CWE Name	Source
CWE-440	Expected Behavior Violation	[email protected]
CWE-697	Incorrect Comparison	[email protected]

Affected Products

Product	Versions
nearform fast-jwt	< 6.2.1
CPE cpe:2.3:a:nearform:fast-jwt::::::node.js::* Remediation No remediation found in references.

Change History

4 change records found show changes

Date	Action	Recorded By
Jun 17, 2026	CVE Modified	[email protected]
Jun 17, 2026	CVE Modified	CISA-ADP
Apr 17, 2026	Initial Analysis	[email protected]
Apr 9, 2026	New CVE Received	[email protected]