CVE-2026-54777 in CoreWCF
Summary
by MITRE • 07/09/2026
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.
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Analysis
by VulDB Data Team • 07/09/2026
The vulnerability in CoreWCF affects the NetNamedPipe transport implementation that was ported from Windows Communication Foundation to .NET Core environments. This flaw exists in versions prior to 1.8.1 and 1.9.1 where the system accepts attachments to pre-existing named pipe instances during a specific race condition window. The vulnerability stems from improper synchronization between shared memory GUID publication and actual service named pipe creation processes, creating a temporal gap that malicious actors can exploit for traffic interception.
The technical implementation flaw occurs when NamedPipeListener initializes and attempts to establish communication channels. During this initialization phase, the system publishes a shared memory GUID before creating the actual named pipe instance, leaving a window where an attacker can create their own named pipe with the same identifier. This race condition allows for local privilege escalation attacks where malicious processes can intercept and potentially modify communications intended for legitimate services. The vulnerability specifically affects the Windows-specific named pipe transport mechanism that CoreWCF implements to enable inter-process communication.
The operational impact of this vulnerability extends beyond simple data interception, as it enables man-in-the-middle attacks against local services that rely on NetNamedPipe transport. Attackers can leverage this weakness to gain unauthorized access to service communications, potentially compromising sensitive data flows and system integrity. This is particularly concerning in enterprise environments where CoreWCF services might be handling confidential information or performing privileged operations through named pipe communication channels.
This vulnerability maps directly to CWE-362, which covers race conditions allowing for concurrent execution of processes with different privileges, and also relates to CWE-284, addressing improper access control mechanisms. From an ATT&CK perspective, this issue aligns with T1068, which involves exploit for privilege escalation, and T1566, covering initial access through spearphishing or other attack vectors that can leverage local system weaknesses. The mitigation strategy requires upgrading to CoreWCF versions 1.8.1 or 1.9.1 where proper synchronization mechanisms have been implemented to prevent the race condition between GUID publication and pipe creation.
The fix implemented in versions 1.8.1 and 1.9.1 addresses this by ensuring that shared memory GUID publication occurs only after the named pipe instance is fully established and ready for communication. This prevents attackers from exploiting the temporal gap where pre-existing pipe instances could be attached to intercept traffic. The implementation change ensures proper atomicity in the initialization sequence, making it impossible for external processes to gain access to the communication channel before legitimate service establishment is complete.
Organizations using CoreWCF should immediately assess their deployment environments to identify systems running vulnerable versions and implement the necessary upgrades as part of their security maintenance protocols. This vulnerability demonstrates the importance of proper synchronization mechanisms in distributed systems and highlights how seemingly minor implementation details can create significant security weaknesses in inter-process communication frameworks. The issue underscores the need for comprehensive testing of race conditions in multi-threaded applications and proper adherence to security best practices during framework porting activities.