I think referencing the well-known cases in cve-rs[1] is quite a bad faith effort. Of course if you try reeeally hard to write unsound code, you can write unsound code. An edge case in the type system downstream of lifetime variance rules is simply not something that matters in any practical attempt to write safe software. I find the tracker interesting since it probes the boundary of the compiler, but it says absolute nothing to the effect of "Rust is unsafe".

[1] https://github.com/Speykious/cve-rs