Incorrect Regular Expression Affecting fast-jwt package, versions <6.2.1
Threat Intelligence
Snyk has a proof-of-concept or detailed explanation of how to exploit this vulnerability.
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Start learning- Snyk IDSNYK-JS-FASTJWT-15965926
- published10 Apr 2026
- disclosed9 Apr 2026
- creditFranciny Rojas
Introduced: 9 Apr 2026
NewCVE-2026-35040 (opens in a new tab)How to fix?
Upgrade fast-jwt to version 6.2.1 or higher.
Overview
fast-jwt is a Fast JSON Web Token implementation
Affected versions of this package are vulnerable to Incorrect Regular Expression in the allowedAud, allowedIss, allowedSub, allowedJti, or allowedNonce options when used with RegExp objects and RegExp is configured with modifiers such as /y and /g. An attacker can cause intermittent authentication failures and potentially trigger retry storms or operational disruptions by repeatedly submitting valid tokens, leading to unpredictable acceptance or rejection outcomes.