Memory corruption via missing Send bound

Data race in the lazy-init crate before 0.4.0 allows attackers to cause memory corruption by sharing a Lazy value across threads. Lazy's unsafe Sync implementation omits a required Send bound on its stored type, so safe code can transfer a Sync but non-Send value between threads. Exploitation requires a consuming Rust program to instantiate Lazy with such a type and exercise it concurrently; resulting behavior can corrupt memory or interrupt the process.