Emacs is a general-purpose programming environment that also implements an editor. By design, it has no internal boundaries. Anything that can run in that environment can read and write the filesystem and process environment, open arbitrary sockets, execute arbitrary commands, and otherwise interact with the local system - and, given TRAMP, also remote systems - as the user under whose account Emacs is running. You don't need to know much of anything about the underlying system to use these capabilities. You just need to know about Emacs. And whatever you do need to know about the underlying system to perform whatever attack you have in mind, Emacs will happily help you learn.

What about RCE in such an environment does not say "game over" to you?