An issue was discovered in the futures-task crate before 0.3.5 for Rust. futures_task::noop_waker_ref allows a NULL pointer dereference.

Affected: crates.io: futures-task

Affected versions of the crate used a `UnsafeCell` in thread-local storage to return a noop waker reference, assuming that the reference would never be returned from another thread.

This resulted in a segmentation fault crash if `Waker::wake_by_ref()` was called on a waker returned from another thread due to it attempting to dereference a pointer that wasn't accessible from the main thread.

Reproduction Example (from issue): ```rust use futures_task::noop_waker_ref; fn main() { let waker = std::thread::spawn(|| noop_waker_ref()).join().unwrap(); waker.wake_by_ref(); } ```

The flaw was corrected by using a `OnceCell::Lazy<>` wrapper around the noop waker instead of thread-local storage.