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dotnet · CoreWCF.PrimitivesCritical

CoreWCF.Primitives Security Vulnerability: Impersonation via TransportWithMessageCredential and WS-SecureConversation

A security vulnerability in CoreWCF.

20 Jun 2026Read 1 minSeverity: act now

What changed

A security vulnerability in CoreWCF.Primitives allows impersonation of authenticated Windows principals when using TransportWithMessageCredential with Windows client credentials and WS-SecureConversation sessions.

Who it affects

Applications using CoreWCF with security mode TransportWithMessageCredential, client credential type Windows, and session establishment (WS-SecureConversation).

What to do today

Upgrade to CoreWCF v1.9.1 or ensure communication is protected by SSL/TLS to prevent capturing of SCT negotiation handshake.

The trail
Collected Audited Written Published