crossbeam-utils provides atomics, synchronization primitives, scoped threads, and other utilities for concurrent programming in Rust. crossbeam-utils prior to version 0.8.7 incorrectly assumed that the alignment of "{i,u}64" was always the same as "Atomic{I,U}64". However, the alignment of "{i,u}64" on a 32-bit target can be smaller than "Atomic{I,U}64". This can cause unaligned memory accesses and data race. Crates using "fetch_*" methods with "AtomicCell<{i,u}64>" are affected by this issue. 32-bit targets without "Atomic{I,U}64" and 64-bit targets are not affected by this issue. This has been fixed in crossbeam-utils 0.8.7. There are currently no known workarounds.