Has there ever existed a C or C++ codebase of significant size that hasn't had exploitable memory corruption issues? I don't think we can keep saying it's a question of the dev's passion or skill or whatever, if no dev has ever managed to do it.

That's not to say memory corruption issues are the only kind of issues, and rewriting a mature C/C++ codebase into a memory safe language may well introduce more issues than it fixes...