---
id: CVE-2026-107719
title: fast-jwt provides fast JSON Web Token (JWT) implementation
summary: >-
  fast-jwt provides fast JSON Web Token (JWT) implementation. Prior to 6.3.4,
  the fast-jwt createVerifier cache can continue accepting a previously valid,
  signed JWT after its exp time when caching is enabled and the token has exp
  but no i…
severity: medium
cvss: 4.2
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:N'
cwe:
  - CWE-613
vendor: fast-jwt
product: fast-jwt
affected:
  - fast-jwt <= 6.3.3
patched:
  - fast-jwt 6.3.4
published: '2026-10-08'
updated: '2026-10-08'
sourceUpdated: '2026-10-08T22:17:28.053'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-107719'
references:
  - url: >-
      https://github.com/nearform/fast-jwt/commit/fc1ddbbe5ce38066ba2cea0b0ce0233932757167
    label: security-advisories@github.com
  - url: 'https://github.com/nearform/fast-jwt/releases/tag/v6.3.4'
    label: security-advisories@github.com
  - url: >-
      https://github.com/nearform/fast-jwt/security/advisories/GHSA-x937-hj6v-793p
    label: security-advisories@github.com
  - url: 'https://github.com/advisories/GHSA-x937-hj6v-793p'
tags:
  - nvd
  - ghsa
  - npm
aliases:
  - GHSA-x937-hj6v-793p
ecosystem: npm
ingestedAt: '2026-10-08T22:11:53.869Z'
---

## Overview

fast-jwt provides fast JSON Web Token (JWT) implementation. Prior to 6.3.4, the fast-jwt createVerifier cache can continue accepting a previously valid, signed JWT after its exp time when caching is enabled and the token has exp but no iat. In src/verifier.js, cacheSet derives the exp cache deadline only when iat is present, so the cache falls back to cacheTTL, and a later cache hit returns the saved payload before verifyToken rechecks expiration. An attacker who can replay the same cached bearer token can extend access until the cache entry expires, but cannot forge a token through this issue. This issue is fixed in version 6.3.4.

## Remediation

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

## Package advisory (CVE-2026-107719)

Affected packages:

- `fast-jwt <= 6.3.3`

Patched in:

- `fast-jwt 6.3.4`

Source: https://github.com/advisories/GHSA-x937-hj6v-793p