# RUSTSEC-2026-0267: Panic-safety unsoundness in `BitVecCore::clear` (double-free / use-after-free)

> A panic during element drop in BitVecCore::clear causes double-free and use-after-free, allowing memory corruption or crashes in applications using stable-vec.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Not stated
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 24 Aug 2026
- **Also known as:** GHSA-mr2v-63pc-gmr4

## What is RUSTSEC-2026-0267?

RUSTSEC-2026-0267 is an use after free vulnerability in stable-vec, published on 24 Aug 2026. 

### Official description

`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](https://github.com/LukasKalbertodt/stable-vec/security/advisories/GHSA-mr2v-63pc-gmr4)
and the 0.4.3 changelog for the full list.

## Which versions are affected by RUSTSEC-2026-0267?

1 open source package ship an affected version, including stable-vec.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `stable-vec` | crates.io | From 0.0.0-0 | 0.4.3 |

## How do I fix RUSTSEC-2026-0267?

Upgrade stable-vec to 0.4.3 or later.

## Is RUSTSEC-2026-0267 being exploited?

There is no known exploitation of RUSTSEC-2026-0267 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for RUSTSEC-2026-0267 and fix it if it is affected.

What it is: RUSTSEC-2026-0267 is an use after free vulnerability in stable-vec, published on 24 Aug 2026. 
Exploitation: There is no known exploitation of RUSTSEC-2026-0267 in the wild and no public exploit code.

Affected packages and fixed versions:
- stable-vec (crates.io): affected from 0.0.0-0; fixed in 0.4.3

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/RUSTSEC-2026-0267/ (Markdown: https://insights.sbomify.com/RUSTSEC-2026-0267/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/RUSTSEC-2026-0267

---
From sbomify Insights: https://insights.sbomify.com/RUSTSEC-2026-0267/
Summaries are generated and may contain mistakes; the official description above is the record.