Medium [CVE-2026-54431] DPoP verifier accepts malformed proof with private key material
This medium-severity Red Hat Linux advisory covers CVE-2026-54431.
Aggregated and source-linked by VulniPulse. Data sources, validation and limitations.
VulniPulse record published Record updated
Summary
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 A flaw was found in liboauth2. This vulnerability could allow an attacker to bypass the intended proof-of-possession mechanism.
A flaw in liboauth2's DPoP verifier allows it to accept malformed proofs containing private key material, contrary to RFC 9449. The impact is limited to applications that implement DPoP using liboauth2 and do not perform additional validation.
Red Hat severity: Moderate — CVSS 5.3 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N). Weakness: CWE-358.
Is CVE-2026-54431 exploited?
No exploitation is reported in the sources VulniPulse tracks: CVE-2026-54431 is not in the CISA KEV catalog (checked ) and this advisory does not report exploitation. That is not proof the vulnerability cannot be exploited.
How do I fix CVE-2026-54431?
Upgrade to a fixed release named by Red Hat:
- 2.3.0
Confirm against the vendor advisory before you patch.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative. Check it before change work.
Official advisory · high-confidence parse· fetched 11 days ago·verify at source
Mitigation checklist
- Ensure DPoP client implementations do not include private key material in the JWK header of DPoP proofs. Review client code to verify only the public key is serialized into the proof's jwk header field. Upgrade liboauth2 to version 2.3.0 or later, which adds server-side rejection of proofs containing private key material per RFC 9449 section 4.3.
Official advisory · high-confidence parse· fetched 11 days ago·verify at source
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