CVE-2026-54776 CoreWCF: Unix Domain Socket PosixIdentity transport accepts connections that skip the security upgrade
Attackers can bypass identity checks in CoreWCF Unix Domain Socket services by skipping security upgrades, requiring specific PosixIdentity configurations.
- 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-2026-54776?
CVE-2026-54776 is a medium-severity authentication bypass 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, a CoreWCF service hosted on Unix Domain Sockets with PosixIdentity client credentials can accept connections that skip the application/unixposix stream upgrade before dispatching messages, bypassing framing-layer identity checks in UnixPosixIdentitySecurityUpgradeProvider. This issue is fixed in versions 1.8.1 and 1.9.1.
Weakness: CWE-306
Which versions are affected by CVE-2026-54776?
4 open source packages ship an affected version, including CoreWCF.UnixDomainSocket.
| Package | Affected | Fixed in |
|---|---|---|
CoreWCF.UnixDomainSocket NuGet | All versions | 1.8.1 |
CoreWCF.UnixDomainSocket NuGet | All versions | 1.8.1 |
CoreWCF.UnixDomainSocket NuGet | From 1.9.0 | 1.9.1 |
CoreWCF.UnixDomainSocket NuGet | From 1.9.0 | 1.9.1 |
How do I fix CVE-2026-54776?
Upgrade CoreWCF.UnixDomainSocket to a fixed version for your release line: 1.8.1 or 1.9.1.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-54776 being exploited?
There is no known exploitation of CVE-2026-54776 in the wild and no public exploit code.
Sources
Also known as GHSA-wjpq-6766-7f5j.