CVE-2026-54784: Corewcf

High severity, CVSS 7.4. EPSS: 0.3% chance of exploitation in the next 30 days.

CoreWCF is a port of the service side of Windows Communication Foundation (WCF) to .NET Core. In version 1.9.0, CoreWCF SPNEGO SecurityContextToken negotiation can expose the proof key recovered from the RSTR when TransportWithMessageCredential with Windows client credentials and session establishment are used, allowing an observer to impersonate the authenticated Windows principal and decrypt or forge WS-SecureConversation traffic. This issue is fixed in version 1.9.1.

Affected products

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

Published 2026-07-08. Last modified 2026-07-10.