Segfaults happen, you run valgrind/asan/tsan etc.
As long as the codebase is not horrendous its easy to fix.
Third party packages complicate things, have to choose/use wisely/appropriately
In Rust they are really rare. Like vanishingly small numbers of them. C++ definitely. SegFaults happen. Sometimes they are even in prod. Rust not so much.
So far there isn't that much stuff written in Rust, so, any non-trivial Rust program will link with a bunch of non-Rust code. On the project I worked on, we had to link with SPDK for example (a rather big iSCSI server implementation).
C++ has been around for... what?.. 40 odd years? And any non-trivial project still links with C libraries.
I don't see this problem somehow going away in Rust w/o some revolutionary changes in operating systems, which is the major supplier of decrepit but unavoidable libraries you have to link with in order to get anything done.