Affected versions of this crate implement Send/Sync for
ArcGuard<RC, T> with no trait bounds on
RC. This allows users to send
RC: !Send to other threads and also allows users to concurrently access
Rc: !Sync from multiple threads.
This can result in memory corruption from data race or other undefined behavior caused by sending
T: !Send to other threads (e.g. dropping
MutexGuard<T> in another thread that didn’t lock its mutex).