Double free in `AlignedBox<[T]>::realloc_with_default` when an element's `Drop` panics

Overview

Shrinking an AlignedBox<[T]> takes ownership of the buffer out of self.container with ManuallyDrop::take, destroys the elements past the new length, and only then commits the new Box back into self.container. ManuallyDrop::take moves ownership but not the bits, so until that commit self.container still points at the original buffer.

T::drop runs inside the destruction loop and is user code — T carries no bound that would exclude a panicking Drop. If it unwinds, the commit is skipped and self.container is left pointing at the buffer whose tail has already been destroyed. AlignedBox's own destructor then reconstructs a Box from that pointer, drops every element again and deallocates — a double free (CWE-415) / use-after-free (CWE-416) reachable from safe Rust.

Growing the slice destroys nothing and is unaffected, as is realloc_with_value, which requires T: Copy and therefore a Drop that cannot run.

Mitigation

Update to 0.3.1.

Affected packages

• aligned_box >= 0.0.0-0, < 0.3.1

Remediation

Upgrade to a patched release:

• aligned_box 0.3.1