The majority of security vulnerabilities in languages like C that aren’t memory safe are due to memory safety issues like UAF, buffer overflows etc etc. I don’t think I’ve seen finer grained research that tries to break it out by class of memory safety issue. The data is something like 80% of reported vulnerabilities in code written in these languages are due to memory safety issues. This doesn’t mean there aren’t other issues. It just means that it’s the cheapest exploit to search for when you are trying to break into a C/C++ service.

And in terms of how easy it is to convert a memory safety issue into an exploit, it’s not meaningfully much harder. The harder pieces are when sandboxing comes into play so that for example exploiting V8 doesn’t give you arbitrary broader access if the compromised process is itself sandboxed.