---
title: "CVE-2026-107720: fast-jwt - Authentication Bypass"
description: "fast-jwt < 6.3.1 contains an authentication bypass caused by accepting unsigned JWTs when key is empty or null and algorithms allowlist is non-empty, letting attackers bypass signature verification and submit arbitrary claims."
url: https://panop.io/threat-heartbeat/CVE-2026-107720/
---

# CVE-2026-107720 fast-jwt - Authentication Bypass

fast-jwt < 6.3.1 contains an authentication bypass caused by accepting unsigned JWTs when key is empty or null and algorithms allowlist is non-empty, letting attackers bypass signature verification and submit arbitrary claims.

CVSS base score 7.4 /10

High

CISA KEV

Not listed

Public exploit

None known

Authentication

Not required

EPSS

0.26% chance of exploitation in 30 days

[View the NVD record ↗](https://nvd.nist.gov/vuln/detail/CVE-2026-107720)

## Details

Type

Authentication Bypass

Impact

Broken Authentication

CVSS vector

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

Published

8 October 2026

Updated

15 October 2026

Weakness

[CWE-20](https://cwe.mitre.org/data/definitions/20.html)

## Vendor fix

Update to version 6.3.1 or later.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

## References

- [https://nvd.nist.gov/vuln/detail/CVE-2026-107720](https://nvd.nist.gov/vuln/detail/CVE-2026-107720)
- [https://github.com/nearform/fast-jwt/pull/649](https://github.com/nearform/fast-jwt/pull/649)
- [https://github.com/nearform/fast-jwt/releases/tag/v6.3.1](https://github.com/nearform/fast-jwt/releases/tag/v6.3.1)
- [https://github.com/nearform/fast-jwt/security/advisories/GHSA-8wpc-h4q6-8fxv](https://github.com/nearform/fast-jwt/security/advisories/GHSA-8wpc-h4q6-8fxv)
- [https://github.com/nearform/fast-jwt/commit/e22a151e83bf6d5e54e281216982d204d5665534](https://github.com/nearform/fast-jwt/commit/e22a151e83bf6d5e54e281216982d204d5665534)

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## What this record can't tell you

- Whether you run the affected software, and where
- Whether an attacker can actually reach and exploit it
- The misconfigurations that never get a CVE number
- What it would cost the business, ranked into what to fix first

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