CVE-2026-54431

Improper Data Validation in liboauth2

State: Published
Severity: 5.1 Medium
Published: Jul 2, 2026
Updated: Jul 2, 2026
Reserved: Jun 15, 2026

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

Scores

CVSS	Score	Vector	Source
4.0	5.1 Medium	CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N	CERT-PL

Weaknesses

CWE-358 Improperly Implemented Security Check for Standard

Affected Products

Product	Versions
liboauth2OpenIDC	before 2.3.0Affected

References

https://cert.pl/en/posts/2026/07/CVE-2026-54430third-party-advisory
https://github.com/OpenIDC/liboauth2product
https://github.com/OpenIDC/liboauth2/commit/c0b57152ed6a0af33aeb04a60bd7f5bff5ab8800issue-tracking

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