The Rust crate 'cmov' contains a vulnerability in its aarch64 implementation of the Cmov and CmovEq functions. The issue arises because high bits of registers are not correctly handled when loading values smaller than the register size, causing conditional move operations to produce incorrect results if those high bits are set. This affects versions from 0.1.1 up to but not including 0.5.4. No known exploits exist, and the impact depends on how the crate is used in specific contexts.