RUSTSEC-2020-0161: `array!` macro is unsound in presence of traits that implement methods it calls internally

What to do

1. See which version you have: cargo tree -i array-macro (it also shows which of your dependencies pulls it in).
2. Update within your version requirement: cargo update -p array-macro. If the fix is a newer major or minor than your requirement allows, raise it in Cargo.toml (for example array-macro = "1.0.5") or update the dependency that pulls it in.
3. Check again with cargo audit, or paste your Cargo.lock into our Cargo.toml checker.

Details from the advisory

Affected versions of this crate called some methods using auto-ref. The affected code looked like this.

let mut arr = $crate::__core::mem::MaybeUninit::uninit();
let mut vec = $crate::__ArrayVec::<T>::new(arr.as_mut_ptr() as *mut T);

In this case, the problem is that as_mut_ptr is a method of &mut MaybeUninit, not MaybeUninit. This made it possible for traits to hijack the method calls in order to cause unsoundness.

trait AsMutPtr<T> {
    fn as_mut_ptr(&self) -> *mut T;
}
impl<T> AsMutPtr<T> for std::mem::MaybeUninit<T> {
    fn as_mut_ptr(&self) -> *mut T {
        std::ptr::null_mut()
    }
}
array![0; 1];

The flaw was corrected by explicitly referencing variables in macro body in order to avoid auto-ref.

References

• Package: crates.io/crates/array-macro
• Advisory: rustsec.org/advisories/RUSTSEC-2020-0161.html
• Web: gitlab.com/KonradBorowski/array-macro/-/commit/01940637dd8f3bfeeee3faf9639fa9ae52f19f4d

From the RustSec Advisory Database (CC0-1.0) via the OSV export, downloaded Oct 24, 2026. Severity score computed from the published CVSS vector.

Other advisories for array-macro

• UnsoundRUSTSEC-2022-0017 · 2022-04-27`array!` macro is unsound when its length is impure constant

Full security history of array-macro