Is CVE-2026-35040 actively exploited?

No active exploitation of CVE-2026-35040 has been confirmed so far. Continue monitoring, as exploit status can change.

Can CVE-2026-35040 be exploited remotely?

Yes. CVE-2026-35040 is exploitable remotely over the network (CVSS attack vector: Network).

What is the CVSS score of CVE-2026-35040?

CVE-2026-35040 has a CVSS score of 5.3 (MEDIUM).

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MEDIUM

CVE-2026-35040

CWE-440Published: April 9, 2026· Updated: Apr 13, 2026

5.3

CVSS v3.1

EPSS:0.06%probability of exploitation in 30 daysPercentile:19.0th

Official 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.

NVD Source

Technical Analysis

CVE-2026-35040 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

The vulnerability requires no privileges and no user interaction, making it a prime target for automated exploitation campaigns and worm-like propagation.