T1191.md

T1191 - CMSTP

Description from ATT&CK

The Microsoft Connection Manager Profile Installer (CMSTP.exe) is a command-line program used to install Connection Manager service profiles. (Citation: Microsoft Connection Manager Oct 2009) CMSTP.exe accepts an installation information file (INF) as a parameter and installs a service profile leveraged for remote access connections.

Adversaries may supply CMSTP.exe with INF files infected with malicious commands. (Citation: Twitter CMSTP Usage Jan 2018) Similar to Regsvr32 / ”Squiblydoo”, CMSTP.exe may be abused to load and execute DLLs (Citation: MSitPros CMSTP Aug 2017) and/or COM scriptlets (SCT) from remote servers. (Citation: Twitter CMSTP Jan 2018) (Citation: GitHub Ultimate AppLocker Bypass List) (Citation: Endurant CMSTP July 2018) This execution may also bypass AppLocker and other whitelisting defenses since CMSTP.exe is a legitimate, signed Microsoft application.

CMSTP.exe can also be abused to Bypass User Account Control and execute arbitrary commands from a malicious INF through an auto-elevated COM interface. (Citation: MSitPros CMSTP Aug 2017) (Citation: GitHub Ultimate AppLocker Bypass List) (Citation: Endurant CMSTP July 2018)

Atomic Tests

• Atomic Test #1 - CMSTP Executing Remote Scriptlet

• Atomic Test #2 - CMSTP Executing UAC Bypass

Atomic Test #1 - CMSTP Executing Remote Scriptlet

Adversaries may supply CMSTP.exe with INF files infected with malicious commands

Supported Platforms: Windows

Inputs

Name	Description	Type	Default Value
inf_file_path	Path to the INF file	path	T1191.inf

Run it with command_prompt!

cmstp.exe /s #{inf_file_path}

Atomic Test #2 - CMSTP Executing UAC Bypass

Adversaries may invoke cmd.exe (or other malicious commands) by embedding them in the RunPreSetupCommandsSection of an INF file

Supported Platforms: Windows

Inputs

Name	Description	Type	Default Value
inf_file_uac	Path to the INF file	path	T1191_uacbypass.inf

Run it with command_prompt!

cmstp.exe /s #{inf_file_uac} /au