---
id: CVE-2026-107721
title: fast-jwt provides fast JSON Web Token (JWT) implementation
summary: >-
  fast-jwt provides fast JSON Web Token (JWT) implementation. Prior to 6.3.0,
  fast-jwt createVerifier accepts Infinity for clockTolerance because its option
  validation checks type and negativity but not finiteness. In
  validateClaimDateValu…
severity: medium
cvss: 5.9
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:N'
cwe:
  - CWE-613
  - CWE-682
vendor: fast-jwt
product: fast-jwt
affected:
  - fast-jwt <= 6.2.4
patched:
  - fast-jwt 6.3.0
published: '2026-10-08'
updated: '2026-10-08'
sourceUpdated: '2026-10-08T22:17:28.410'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-107721'
references:
  - url: >-
      https://github.com/nearform/fast-jwt/commit/c0fb5b88b4c88ff2bdd194ca2c713599ad9e38b6
    label: security-advisories@github.com
  - url: 'https://github.com/nearform/fast-jwt/releases/tag/v6.3.0'
    label: security-advisories@github.com
  - url: >-
      https://github.com/nearform/fast-jwt/security/advisories/GHSA-687g-22h4-j4w4
    label: security-advisories@github.com
  - url: 'https://github.com/advisories/GHSA-687g-22h4-j4w4'
tags:
  - nvd
  - ghsa
  - npm
aliases:
  - GHSA-687g-22h4-j4w4
ecosystem: npm
ingestedAt: '2026-10-08T22:11:53.873Z'
---

## Overview

fast-jwt provides fast JSON Web Token (JWT) implementation. Prior to 6.3.0, fast-jwt createVerifier accepts Infinity for clockTolerance because its option validation checks type and negativity but not finiteness. In validateClaimDateValue, infinite positive and negative modifiers make exp and nbf comparisons always pass, allowing expired or not-yet-active tokens to be accepted. The verifier cache also derives infinite bounds, so entries created under this configuration can remain valid until eviction. Exploitation requires an application administrator or equivalent configuration path to set clockTolerance to Infinity. This issue is fixed in version 6.3.0.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

## Package advisory (CVE-2026-107721)

Affected packages:

- `fast-jwt <= 6.2.4`

Patched in:

- `fast-jwt 6.3.0`

Source: https://github.com/advisories/GHSA-687g-22h4-j4w4