Well, the ability to call a set of functions (really, to overwrite a vtable pointer with a constrained set of values - which is a table of function pointers you

Well, the ability to call a set of functions (really, to overwrite a vtable pointer with a constrained set of values - which is a table of function pointers your C++ compiler emits to handle virtual function calls) is the underlying vulnerability. The article describes a proof of concept exploit - an approach of turning this into a concrete security problem (arbitrary command execution/calling libc).