CVE-2026-54784 CoreWCF: SPNEGO SecurityContextToken proof key wrapped without confidentiality
An attacker can impersonate authenticated users and decrypt traffic due to insufficient protection of SPNEGO proof keys in CoreWCF.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-54784?
CVE-2026-54784 is a high-severity vulnerability in CoreWCF, published on 8 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
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.
Which versions are affected by CVE-2026-54784?
2 open source packages ship an affected version, including CoreWCF.Primitives.
| Package | Affected | Fixed in |
|---|---|---|
CoreWCF.Primitives NuGet | From 1.9.0 | 1.9.1 |
CoreWCF.Primitives NuGet | From 1.9.0 | 1.9.1 |
How do I fix CVE-2026-54784?
Upgrade CoreWCF.Primitives to 1.9.1 or later.
Is CVE-2026-54784 being exploited?
There is no known exploitation of CVE-2026-54784 in the wild and no public exploit code.
Sources
Also known as GHSA-2288-8h3r-cqgg.