# RUSTSEC-2026-0284: Double free in `Map::into_iter` and an uninitialized `Arc` in `SharedIncin::clear` > Safe Rust code can trigger double frees or use uninitialized memory in concurrent data structures, potentially leading to crashes or arbitrary code execution. - **Severity:** Not scored - **Exploited in the wild:** Not known - **Login needed:** Not needed - **Attackable:** Not stated - **Victim action needed:** Not needed - **Fix available:** No - **Published:** 26 Aug 2026 ## What is RUSTSEC-2026-0284? RUSTSEC-2026-0284 is an use after free vulnerability in lockfree, published on 26 Aug 2026. ### Official description Two independent soundness problems, both reachable from safe Rust. `Map::into_iter` drops `builder` (the caller-supplied hasher `H`) and `incin` by hand, then commits the ownership transfer with `mem::forget(self)`. `H::drop` is user code and may panic. If it does, `mem::forget(self)` is skipped and the still-live `Map` unwinds, whose field drop glue destroys `builder` a second time. An empty map is enough — no entries or concurrency required. `SharedIncin::clear` writes `mem::uninitialized::>()` into `self.inner` before taking the real `Arc` out. `Arc` has a validity invariant, so this is undefined behaviour at the point of creation, with no panic or concurrency involved. Between that write and the repairing one, `self.inner` also holds garbage while `self` is still droppable, so an unwind from `incin.clear()` or `Arc::new` decrements a refcount through an uninitialized pointer. The `make_shared_incin!` macro is instantiated five times, so this covers `queue`, `stack`, `map`, `channel::spmc` and `channel::mpmc`. ## 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`. * CWE-908 (Use of Uninitialized Resource): an `Arc` is constructed from uninitialized bytes. ## Fix No fixed release is available. The crate has had no release since 2018-11-18 and the maintainer has not responded to the report. ## Which versions are affected by RUSTSEC-2026-0284? 1 open source package ship an affected version, including lockfree. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `lockfree` | crates.io | From 0.0.0-0 | None | ## How do I fix RUSTSEC-2026-0284? No fix has been published for RUSTSEC-2026-0284 yet. Limit exposure of the affected software until one is available. ## Is RUSTSEC-2026-0284 being exploited? There is no known exploitation of RUSTSEC-2026-0284 in the wild and no public exploit code. ## Fix prompt for AI coding agents ```text Check this codebase for RUSTSEC-2026-0284 and fix it if it is affected. What it is: RUSTSEC-2026-0284 is an use after free vulnerability in lockfree, published on 26 Aug 2026. Exploitation: There is no known exploitation of RUSTSEC-2026-0284 in the wild and no public exploit code. Affected packages and fixed versions: - lockfree (crates.io): affected from 0.0.0-0; no fix listed 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-2026-0284/ (Markdown: https://insights.sbomify.com/RUSTSEC-2026-0284/index.md) ``` ## Sources - OSV: https://osv.dev/vulnerability/RUSTSEC-2026-0284 --- From sbomify Insights: https://insights.sbomify.com/RUSTSEC-2026-0284/ Summaries are generated and may contain mistakes; the official description above is the record.