CVE-2026-54781: Corewcf

High severity, CVSS 7.4. EPSS: 0.2% chance of exploitation in the next 30 days.

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.

Affected products

• Corewcf Corewcf: from 1.9.0, before 1.9.1 (fixed in 1.9.1); before 1.8.1 (fixed in 1.8.1)

Published 2026-07-08. Last modified 2026-07-09.