---
id: CVE-2026-107723
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 a validly signed JWT whose payload is a JSON
  array because src/decoder.js checks that the payload is an object but does not
  rejec…
severity: high
cvss: 8.1
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N'
cwe:
  - CWE-1287
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: '2026-10-08T22:17:28.757'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-107723'
references:
  - url: >-
      https://github.com/nearform/fast-jwt/commit/86e83efd8b5244f50859532d99244f0a9a9a4368
    label: security-advisories@github.com
  - url: 'https://github.com/nearform/fast-jwt/pull/639'
    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-5hjw-83fp-phq9
    label: security-advisories@github.com
  - url: 'https://github.com/advisories/GHSA-5hjw-83fp-phq9'
tags:
  - nvd
  - ghsa
  - npm
aliases:
  - GHSA-5hjw-83fp-phq9
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 a validly signed JWT whose payload is a JSON array because src/decoder.js checks that the payload is an object but does not reject arrays. The claim validator loop then finds no named exp, nbf, iss, aud, sub, jti, or nonce properties and silently skips those configured checks, returning the array as a successfully verified payload. An attacker who can produce or influence a validly signed token may bypass expiry, issuer, audience, subject, revocation, and replay protections. The opt-in requiredClaims option can block missing claims, and signature verification itself is not bypassed. 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-2026-107723)

Affected packages:

- `fast-jwt <= 6.2.4`

Patched in:

- `fast-jwt 6.3.0`

Source: https://github.com/advisories/GHSA-5hjw-83fp-phq9