CVE-2026-54777 CoreWCF NetNamedPipe transport accepts attach to a pre-existing named pipe instance
Local attackers can intercept NetNamedPipe traffic by racing service startup, exposing sensitive data in CoreWCF applications.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-54777?
CVE-2026-54777 is a medium-severity vulnerability in CoreWCF, published on 8 Jul 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
CoreWCF is a port of the service side of Windows Communication Foundation (WCF) to .NET Core. Prior to 1.8.1 and 1.9.1, CoreWCF NetNamedPipe transport accepts attachment to a pre-existing named pipe instance, allowing local interception of NetNamedPipe traffic when an attacker races NamedPipeListener startup between shared memory GUID publication and service named pipe creation. This issue is fixed in versions 1.8.1 and 1.9.1.
Which versions are affected by CVE-2026-54777?
4 open source packages ship an affected version, including CoreWCF.NetNamedPipe.
| Package | Affected | Fixed in |
|---|---|---|
CoreWCF.NetNamedPipe NuGet | All versions | 1.8.1 |
CoreWCF.NetNamedPipe NuGet | All versions | 1.8.1 |
CoreWCF.NetNamedPipe NuGet | From 1.9.0 | 1.9.1 |
CoreWCF.NetNamedPipe NuGet | From 1.9.0 | 1.9.1 |
How do I fix CVE-2026-54777?
Upgrade CoreWCF.NetNamedPipe to a fixed version for your release line: 1.8.1 or 1.9.1.
Is CVE-2026-54777 being exploited?
There is no known exploitation of CVE-2026-54777 in the wild and no public exploit code.
Sources
Also known as GHSA-6jj2-4q5c-x8g6.