CVE-2026-54431
Raw vector
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:XCVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.
Summary
CVE-2026-54431 is a medium-severity Improperly Implemented Security Check for Standard (CWE-358) vulnerability in Cert (inferred from references). Its CVSS base score is 5.1 (Medium).
Operationally, exploitation aligns with the MITRE ATT&CK technique Downgrade Attack (T1689); ranked at the 7th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-41277
- 🇵🇱 CERT-PL: cert.pl
Vulnerability Data
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…
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a malformed DPoP proof that embeds the private Elliptic Curve (EC) key in the header. This issue was fixed in version 2.3.0
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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V17.2.8
Likely Mitigating Controls AI
Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.
Assessments identify and document improperly implemented security checks, allowing fixes that reduce exploitation of flawed checks.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Secure SDLC practices directly require correct implementation of standardized security checks and algorithms.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Security testing in development and acceptance validates that required security checks function as specified.
Use of cryptography control depends on correct implementation of standardized cryptographic checks.
Secure development life cycle mandates verification that security checks required by standards are correctly implemented.
Application security requirements explicitly call for correct implementation of standardized security mechanisms.
Secure system architecture and engineering principles require faithful realization of protocol-level security checks.
Secure coding practices directly address correct implementation of security-relevant checks in standardized algorithms.