GHSA-m7w4-8wp8-m2xq

An issue was discovered in the beef crate before 0.5.0 for Rust. Affected versions of this crate did not have a `T: Sync` bound in the `Send` impl for `Cow<'_, T, U>`. This allows users to create data races by making `Cow` contain types that are (Send && !Sync) like `Cell<_>` or `RefCell<_>`.

Such data races can lead to memory corruption.

The flaw was corrected in commit d1c7658 by adding trait bounds `T: Sync` and `T::Owned: Send` to the `Send` impl for `Cow<'_, T, U>`.