What’s Vulnerable › Vulnerabilities

CVE-2026-54431: Improper Data Validation in liboauth2

• Severity: medium (CVSS 5.1 v4.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-07-02 · updated 2026-10-25
• Weakness: CWE-358

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

Affected products

• OpenIDC liboauth2: before 2.3.0 — fixed in 2.3.0

How to fix

Upgrade to a fixed version: OpenIDC liboauth2 2.3.0. Check the vendor advisory for mitigations.

References

• https://cert.pl/en/posts/2026/07/CVE-2026-54430
• https://github.com/OpenIDC/liboauth2
• https://github.com/OpenIDC/liboauth2/commit/c0b57152ed6a0af33aeb04a60bd7f5bff5ab8800

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