Seagull Software BarTender Unauthenticated RCE via .NET Remoting Service

Seagull Software BarTender 2010, 2016, and 2019 contain an unauthenticated remote code execution vulnerability in the .NET Remoting service exposed on TCP port 7375 via BtSystem.Service.exe. The service registers an unauthenticated singleton endpoint — BarTenderSystem for BarTender 2016 <= R9, and DataServiceSingleton for BarTender 2019 <= R10 — configured with BinaryServerFormatterSinkProvider and TypeFilterLevel set to Full. An unauthenticated remote attacker can exploit .NET Remoting object unmarshalling to read or write arbitrary files on the server using the .NET WebClient class, or coerce NTLMv2 authentication by supplying a UNC path to an attacker-controlled server, enabling sensitive credential disclosure, remote code execution, or lateral movement depending on service account privileges and network environment. The service runs in the context of NT AUTHORITY\\SYSTEM. This vulnerability is corrected in BarTender 12.0.1. Users of affected releases should upgrade to BarTender 12.0.1 or later.