CVE-2026-54431: CWE-358 Improperly Implemented Security Check for Standard in OpenIDC liboauth2
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
AI Analysis
Technical Summary
The vulnerability in liboauth2's DPoP verifier arises because it does not reject proofs whose jwk header contains private key material, contrary to RFC 9449 section 4.3 step 7. Specifically, the oauth2_token_verify() function incorrectly validates a malformed DPoP proof embedding a private Elliptic Curve key in the header, resulting in acceptance of invalid proofs. This improper security check is classified as CWE-358. The issue affects versions of liboauth2 before 2.3.0 and was resolved in version 2.3.0.
Potential Impact
Successful exploitation could lead to acceptance of malformed DPoP proofs containing private key material, potentially undermining the proof-of-possession security guarantees. The CVSS 4.0 base score is 5.1 (medium severity), indicating limited attack vector (local), low complexity, and no user interaction required. There are no known exploits in the wild.
Mitigation Recommendations
Upgrade liboauth2 to version 2.3.0 or later, where this vulnerability has been fixed. No other mitigation guidance is provided or required.
CVE-2026-54431: CWE-358 Improperly Implemented Security Check for Standard in OpenIDC liboauth2
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
CVSS v4.0
Score 5.1medium
Affected software
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Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The vulnerability in liboauth2's DPoP verifier arises because it does not reject proofs whose jwk header contains private key material, contrary to RFC 9449 section 4.3 step 7. Specifically, the oauth2_token_verify() function incorrectly validates a malformed DPoP proof embedding a private Elliptic Curve key in the header, resulting in acceptance of invalid proofs. This improper security check is classified as CWE-358. The issue affects versions of liboauth2 before 2.3.0 and was resolved in version 2.3.0.
Potential Impact
Successful exploitation could lead to acceptance of malformed DPoP proofs containing private key material, potentially undermining the proof-of-possession security guarantees. The CVSS 4.0 base score is 5.1 (medium severity), indicating limited attack vector (local), low complexity, and no user interaction required. There are no known exploits in the wild.
Mitigation Recommendations
Upgrade liboauth2 to version 2.3.0 or later, where this vulnerability has been fixed. No other mitigation guidance is provided or required.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- CERT-PL
- Date Reserved
- 2026-06-15T13:08:01.057Z
- Cvss Version
- 4.0
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6a463f4927e9c79719b5b54f
Added to database: 07/02/2026, 10:36:57 UTC
Last enriched: 07/02/2026, 10:51:16 UTC
Last updated: 07/02/2026, 11:36:54 UTC
Views: 8
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