CVE-2026-54431

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

Affected Software

Weaknesses

• CWE-358: CWE-358 Improperly Implemented Security Check for Standard

ADP Enrichment

CISA ADP Vulnrichment

• SSVC:
• Exploitation: none
  • Automatable: no
  • Technical Impact: partial

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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