Quick answers
- Is CVE-2026-120459 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-120459 being exploited in the wild.
- How severe is CVE-2026-120459?
- High severity, with a CVSS score of 7.4, published 2 November 2026.
- Which products and versions are affected?
- Mpdavis Python-Jose through 3.5.0.
- Is there a fix for CVE-2026-120459?
- No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
- How is CVE-2026-120459 attacked?
- It is attacked over the network, in a software library.
- Am I affected by CVE-2026-120459?
- Check whether you run Mpdavis Python-Jose at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
Technical details
The HMACKey and CryptographyHMACKey classes accept zero-length HMAC secrets without validation. When an application's HS256/HS384/HS512 verification key resolves to an empty value (e.g., an oct JWK with empty k field), an attacker can compute a valid HMAC signature for any token payload, which jwt.decode will accept. This is a cryptographic bypass that requires only network access to the affected application.
Affected products
- mpdavis python-jose through 3.5.0
Timeline
- 2026-11-02: disclosed