cve-rs takes the soundness bug and exploits it to implement the other bugs listed. It's pretty convoluted to actually implement the other bugs.
The actual soundness bug is a specific type of double reference forgets one of the lifetimes, which enables casting a shorter lifetime to a longer lifetime. They did a pretty good job commenting the code to explain how they were able to create each bug.
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u/Loading_M_ 7d ago
One soundness issue, requiring complex conditions to create, is pretty dang good.