Modern C++ does not mandate that every value be a valid instance of its type wherever it is theoretically accessible, so I'm not sure why you're saying modern C++ fixes this. Actually, the fact that Rust does is something people somewhat regularly complain about. It is a heavy-handed performance / code complexity vs. safety tradeoff that certainly fixes this bug, which I think is a pretty reasonable thing to point out.
If you follow C++14 core guidelines, the defect described would not have occurred. The bug at its core is usage of unsanitized input data. You don't need to "mandate that every value be a valid instance of its type wherever it is theoretically accessible", however that may differ from simple sane C++14 paradigms.
OPINION ALERT: Honestly guys get over rust, it does not offer a single advantage in real-life programming scenarios.