CVE-2026-54431 Improper Data Validation in liboauth2
Attackers can bypass DPoP proof validation by embedding private keys in the JWK header, allowing unauthorized token usage.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-54431?
CVE-2026-54431 is a medium-severity vulnerability in OpenIDC liboauth2, published on 2 Jul 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In liboauth2 the Demonstrating Proof-of-Possession (DPoP) verifier accepts a proof whose JSON Web Key (jwk) header contains private key material. RFC 9449 section 4.3 step 7 requires the verifier to reject such a proof but oauth2_token_verify() function returns success for a malformed DPoP proof that embeds the private Elliptic Curve (EC) key in the header.
This issue was fixed in version 2.3.0
Weakness: CWE-358
Which versions are affected by CVE-2026-54431?
How do I fix CVE-2026-54431?
Upgrade to a fixed version.
Is CVE-2026-54431 being exploited?
There is no known exploitation of CVE-2026-54431 in the wild and no public exploit code.
Sources
Also known as AZL-91682, DEBIAN-CVE-2026-54431, GHSA-3pf6-g4x4-jm46, UBUNTU-CVE-2026-54431.