Windows Exploitation Tricks: Relaying DCOM Authentication

The technique to locally relay authentication for DCOM was something I originally reported back in 2015 (issue 325). This issue was fixed as CVE-2015-2370, however the underlying authentication relay using DCOM remained. This was repurposed and expanded upon by various others for local and remote privilege escalation in the RottenPotato series of exploits, the latest in that line being RemotePotato which is currently unpatched as of October 2021.

The key feature that the exploit abused is standard COM marshaling. Specifically when a COM object is marshaled so that it can be used by a different process or host, the COM runtime generates an OBJREF structure, most commonly the OBJREF_STANDARD form. This structure contains all the information necessary to establish a connection between a COM client and the original object in the COM server.