It wouldn't cause the problem in itself perhaps, but I find it a bit reductive to look at the type in isolation like that. Sometime, somewhere, someone will call std::vector<T,Allocator>::data on that vector and use the resulting pointer as the src argument to memcpy (or some other function), and someone else will make a change that causes an overflow of the dst buffer. Shit happens and code written in modern C++ also has bugs and some of those bugs have security implications.