---
title: "CVE-2026-120459: python-jose - Authentication Bypass"
description: "python-jose <= 3.5.0 contains an authentication bypass caused by acceptance of zero-length HMAC secrets in HMACKey and CryptographyHMACKey, letting unauthenticated attackers forge JWTs with arbitrary claims, exploit requires empty verification key."
url: https://panop.io/threat-heartbeat/CVE-2026-120459/
---

# CVE-2026-120459 python-jose - Authentication Bypass

python-jose <= 3.5.0 contains an authentication bypass caused by acceptance of zero-length HMAC secrets in HMACKey and CryptographyHMACKey, letting unauthenticated attackers forge JWTs with arbitrary claims, exploit requires empty verification key.

CVSS base score 7.4 /10

High

CISA KEV

Not listed

Public exploit

None known

Authentication

Not required

[View the NVD record ↗](https://nvd.nist.gov/vuln/detail/CVE-2026-120459)

## 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

2 November 2026

Updated

3 November 2026

Weakness

[CWE-347](https://cwe.mitre.org/data/definitions/347.html)

## Vendor fix

Update to a version later than 3.5.0 or the latest available version.

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-2026-120459](https://nvd.nist.gov/vuln/detail/CVE-2026-120459)
- [https://github.com/mpdavis/python-jose/blob/3.5.0/jose/backends/cryptography\_backend.py](https://github.com/mpdavis/python-jose/blob/3.5.0/jose/backends/cryptography_backend.py)
- [https://github.com/mpdavis/python-jose/blob/3.5.0/jose/backends/native.py](https://github.com/mpdavis/python-jose/blob/3.5.0/jose/backends/native.py)
- [https://github.com/mpdavis/python-jose/issues/398](https://github.com/mpdavis/python-jose/issues/398)
- [https://www.vulncheck.com/advisories/python-jose-through-3.5.0-authentication-bypass-via-empty-hmac-key](https://www.vulncheck.com/advisories/python-jose-through-3.5.0-authentication-bypass-via-empty-hmac-key)

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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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