Cross-compiling OpenSSL to Rust and then compiling the Rust would also not get rid of the memory-unsafety vulnerabilities created by writing OpenSSL in C. Neve

Cross-compiling OpenSSL to Rust and then compiling the Rust would also not get rid of the memory-unsafety vulnerabilities created by writing OpenSSL in C. Nevertheless, if you wrote OpenSSL in Rust, or any memory-safe language, it would not have those memory-unsafety vulnerabilities. The same applies when writing in a capability-safe language. It's fairly deliberately ignorant to call these kind of properties "magic".