# RUSTSEC-2026-0331: Panic on Decoding Short Hybrid Keys

> An attacker can cause a denial of service by providing short input slices to key decoding functions in the libcrux-kem library.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 24 Aug 2026

## What is RUSTSEC-2026-0331?

RUSTSEC-2026-0331 is a denial of service vulnerability in libcrux-kem, published on 24 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

The deserialization functions `X25519MlKem768Draft00PrivateKey::decode` `X25519MlKem768Draft00PublicKey::decode` and `XWingKemDraft06PublicKey::decode` would panic during an indexing operation when provided an input slice that is shorter than the length of the given key type, i.e. shorter than 2400 bytes in the case of the `X25519MlKem768Draft00` private key and shorter than 1184 bytes in the case of the `X25519MlKem768Draft` and `XWingKemDraft06` public keys.

# Impact

Applications decoding attacker provided slices into the above mentioned private and public key types could be made to panic.

# Mitigation

With release of version `0.0.10` of `libcrux-kem` this bug has been fixed and the serialization functions return `InvalidPrivateKey` and `InvalidPublicKey` errors on invalid input buffer lengths.

We recommend users upgrade to `libcrux-kem` version `0.0.10`.

## Which versions are affected by RUSTSEC-2026-0331?

1 open source package ship an affected version, including libcrux-kem.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `libcrux-kem` | crates.io | From 0.0.0-0 | 0.0.10 |

## How do I fix RUSTSEC-2026-0331?

Upgrade libcrux-kem to 0.0.10 or later.

## Is RUSTSEC-2026-0331 being exploited?

There is no known exploitation of RUSTSEC-2026-0331 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for RUSTSEC-2026-0331 and fix it if it is affected.

What it is: RUSTSEC-2026-0331 is a denial of service vulnerability in libcrux-kem, published on 24 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of RUSTSEC-2026-0331 in the wild and no public exploit code.

Affected packages and fixed versions:
- libcrux-kem (crates.io): affected from 0.0.0-0; fixed in 0.0.10

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-2026-0331/ (Markdown: https://insights.sbomify.com/RUSTSEC-2026-0331/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/RUSTSEC-2026-0331

---
From sbomify Insights: https://insights.sbomify.com/RUSTSEC-2026-0331/
Summaries are generated and may contain mistakes; the official description above is the record.