High severityGHSA Advisory· Published Jun 19, 2026· Updated Jun 19, 2026
CoreWCF: SPNEGO SecurityContextToken proof key wrapped without confidentiality
CVE-2026-54784
Description
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 keys derived from the SCT.
Preconditions
Using security mode TransportWithMessageCredential with client credential type Windows, along with session establishment (which triggers use of WS-SecureConversation).
Patches
Fixed in CoreWCF v1.9.1
Workarounds
Ensure communication is protected by SSL/TLS to prevent capturing of SCT negotiation handshake.
AI Insight
LLM-synthesized narrative grounded in this CVE's description and references.
Affected packages
Versions sourced from the GitHub Security Advisory.
| Package | Affected versions | Patched versions |
|---|---|---|
CoreWCF.PrimitivesNuGet | >= 1.9.0, < 1.9.1 | 1.9.1 |
Affected products
1Patches
Vulnerability mechanics
References
2News mentions
1- CoreWCF: 13 CVEs Disclosed in a Single Day — Critical SAML Bypass and WS-Security FlawsVypr Intelligence · Jun 19, 2026