Rundll32 is a tool was created by Microsoft Service, the purpose of Rundll32 tool is to use libraries DLL in an operating system, and one of the features in a Rundll32 tool is It grants users simulationn session with functions in DLLs.
Synopsis:
Use rundll32 to invoke CLSID:
&- PoC https://github.com/homjxi0e/ReaCOM/blob/master/Classes/COMScripetlet.reg