GHSA-mr2v-63pc-gmr4

BitVecCore::clear drops every occupied element with drop_in_place and only afterwards clears the occupancy bits and resets len. If an element's Drop panics, those metadata updates are skipped, so the slot of the already-dropped element stays marked as occupied. BitVecCore::drop calls clear() again, visits the same slot, and drops the element a second time — a double-free / use-after-free reachable from safe Rust.

Reachable via the public StableVec::clear and ExternStableVec::clear, which delegate to BitVecCore::clear.

Impact

• CWE-415 (Double Free): the same allocation is freed twice.
• CWE-416 (Use-After-Free): a freed allocation is accessed during a repeated Drop.

Reachable entirely from safe Rust via catch_unwind with element types whose Drop can panic. Confirmed under AddressSanitizer on 0.4.2.

Fix

Fixed in stable-vec 0.4.3 by removing each element via remove_at, which clears the occupancy bit before taking the value out.

Release 0.4.3 also fixes several other panic-safety issues found by the maintainer; see GHSA-mr2v-63pc-gmr4 and the 0.4.3 changelog for the full list.