# RUSTSEC-2026-0410: WebAssembly allocator shim corrupts memory on allocation failure


- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Fix available:** Yes
- **Published:** 16 Oct 2026

## What is RUSTSEC-2026-0410?

RUSTSEC-2026-0410 is a vulnerability in zstd-sys, published on 16 Oct 2026. 

### Official description

On wasm32, zstd-sys provides `malloc` and `free` to the C library through a
shim over Rust's allocator. The shim did not check for allocation failure:
it wrote its size header to address 0 and returned address 4, which the C
library used as a valid buffer. `free(NULL)` also read below address 0.

Whenever the instance cannot grow its memory by what a frame asks for, a
small crafted frame (a 9-byte header declaring a 128 MiB window is enough)
made decompression write decoded data over the bottom of the module's
linear memory, instead of failing. The corruption stays within the wasm
sandbox.

The flaw was corrected by returning NULL on allocation failure or size
overflow, and by making `free(NULL)` a no-op.

## Which versions are affected by RUSTSEC-2026-0410?

1 open source package ship an affected version, including zstd-sys.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `zstd-sys` | crates.io | From 2.0.9 | 2.1.2 |

## How do I fix RUSTSEC-2026-0410?

Upgrade zstd-sys to 2.1.2 or later.

## Is RUSTSEC-2026-0410 being exploited?

There is no known exploitation of RUSTSEC-2026-0410 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for RUSTSEC-2026-0410 and fix it if it is affected.

What it is: RUSTSEC-2026-0410 is a vulnerability in zstd-sys, published on 16 Oct 2026. 
Exploitation: There is no known exploitation of RUSTSEC-2026-0410 in the wild and no public exploit code.

Affected packages and fixed versions:
- zstd-sys (crates.io): affected from 2.0.9; fixed in 2.1.2

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-2026-0410/ (Markdown: https://insights.sbomify.com/RUSTSEC-2026-0410/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/RUSTSEC-2026-0410

---
From sbomify Insights: https://insights.sbomify.com/RUSTSEC-2026-0410/
Summaries are generated and may contain mistakes; the official description above is the record.