CVE-2026-54784 CoreWCF: SPNEGO SecurityContextToken proof key wrapped without confidentiality

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...

CVE-2026-54784

CoreWCF CVE-2026-54784 affects CoreWCF 1.9.0 where SPNEGO SecurityContextToken proof key recovered from the RSTR can be observed when using TransportWithMessageCredential with Windows client credentials, enabling impersonation of the Windows principal and decryption/forgery of WS‑SecureConversati...

CoreWCF: SPNEGO SecurityContextToken proof key wrapped without confidentiality

Impact When the proof key recovered from the RSTR can be observed by a party that is not the legitimate client, that party can impersonate the authenticated Windows principal for the lifetime of the SCT default 10 hours and decrypt or forge any subsequent WS‑SecureConversation traffic that uses...