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CVE-2026-54431

Improper Data Validation in liboauth2

MEDIUM
5.1
CVSS Score
Published: July 2, 2026 at 10:30 AM UTC
Updated: October 25, 2026 at 09:10 PM UTC
1 product affected across 1 vendorLIBOAUTH2

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Severity
MEDIUM5.1
Exploit prediction
EPSS 0.2%
SSVC
No known exploit

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

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

LIBOAUTH2· Openidc
90%
v < 2.3.0
Affected range stops below 2.3.0, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet, and no fixed version or vendor advisory is recorded against it.

References (4)

Source: cverecord
https://cert.pl/en/posts/2026/06/CVE-2026-54430
Product
Source: cverecord
https://github.com/OpenIDC/liboauth2
Issue Tracking
Source: cverecord
https://github.com/OpenIDC/liboauth2/commit/c0b57152ed6a0af33aeb04a60bd7f5bff5ab8800
Third Party Advisory
Source: cverecord
https://cert.pl/en/posts/2026/07/CVE-2026-54430

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

5.1MEDIUMCERT-PL
Vector?

Quick Info

StatusDEFERRED
CWE
CWE-358

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