CVE-2020-36448: Data races in cache

The vulnerability stems from improper trait implementations rather than specific functions. The Cache<K> struct unconditionally implements Send/Sync traits without requiring K to be Send/Sync. This allows non-thread-safe types (e.g., Rc<T>, Cell<T>) to be used in multi-threaded contexts, causing data races. The root cause is the unsafe unsafe impl<K> Send for Cache<K> {} and unsafe impl<K> Sync for Cache<K> {} implementations, which lack trait bounds on K. Since these are trait implementations rather than discrete functions, no specific functions are identified as vulnerable.