Reported

September 22, 2026

Issued

September 22, 2026

Package

stack_collections (crates.io)

Type

Vulnerability

Categories

• memory-corruption

Keywords

#double-free #unwind-safety

References

• https://github.com/OverwrittenCode/stack_collections/pull/4

Patched

• >=0.3.3

Unaffected

• <0.3.0

Description

Summary

StackVec::retain committed its new length to self.len only after its internal loop completed. If the retain predicate or a removed element's Drop implementation panicked before the loop finished, unwinding proceeded with self.len still equal to the original, pre-retain length, leaving either a duplicated or already-destroyed element inside 0..len. StackVec's own Drop then revisited that slot, causing a double-drop (and for heap-owning types, a double-free).

Impact

Affects StackVec<T, CAP>::retain for T: Drop types where the predicate or the removed element's destructor can panic, on builds with unwinding enabled (panic = "unwind"). no_std/panic = "abort" builds cannot trigger this, since unwinding never occurs.

Patch

Fixed in 0.3.3 using an unwind-safe backshift guard, matching the approach alloc::vec::Vec::retain uses.

Advisory available under CC0-1.0 license.