[viraptor]

> What makes implementations of newer languages more immune to heap-use-after-free and heap-buffer-overflow bugs?

Simply the enforced restrictions on memory management. Of course some of those languages are implemented either in C, or in some language which implements that memory management. But if you implement a language with forced GC and bound checks (python for example), you have only two places where use-after-free and overflows can originate. (ignoring native extensions) It's much simpler to review / fix them globally rather than in each usage site. Putting other restrictions like strict type hierarchy, lifetimes, escape analysis, etc. in place makes the languages more immune by design.

Older/newer split doesn't make a huge amount of sense though. There are lisps, there's ADA, there are lots of other very old languages which avoid those issues by design.