CVE-2026-54781 PUBLISHED

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.

• https://github.com/CoreWCF/CoreWCF/security/advisories/GHSA-48pq-2xq3-c2m4
• https://github.com/CoreWCF/CoreWCF/commit/6a99df3242f54acd6f89edfd6050430b72d0c685
• https://github.com/CoreWCF/CoreWCF/commit/86dd3232b6b8aaf32281be9e8d798afad6145d58
• https://github.com/CoreWCF/CoreWCF/commit/9eb9b46d1c2af06fb71f656a02f4d5b4649c1f03
• https://github.com/CoreWCF/CoreWCF/releases/tag/v1.8.1
• https://github.com/CoreWCF/CoreWCF/releases/tag/v1.9.1

• CWE-287: Improper Authentication CWE
• CWE-345: Insufficient Verification of Data Authenticity CWE