Is CVE-2026-54781 being exploited?

No public exploit is currently tracked.

How severe is CVE-2026-54781?

CVE-2026-54781 has a CVSS v3 severity of HIGH (7.4).

Back

CVE-2026-54781

Description

CoreWCF is a port of the service side of Windows Communication Foundation (WCF) to .NET Core. Prior to 1.8.1 and 1.9.1, CoreWCF SAML token validation does not enforce SubjectConfirmation method URIs or holder-of-key proof keys in SamlSecurityTokenHandler, allowing holder-of-key downgrade or custom confirmation method assertions to authenticate a subject without proving authority over the assertion. This issue is fixed in versions 1.8.1 and 1.9.1.