---
id: RUSTSEC-2026-0344
title: 'Decompression bomb in `ruzstd`: a tiny input can exhaust memory (OOM)'
summary: 'Decompression bomb in `ruzstd`: a tiny input can exhaust memory (OOM)'
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'
vendor: ruzstd
product: ruzstd
ecosystem: rust
affected:
  - 'ruzstd >= 0.0.0-0, < 0.9.1'
patched:
  - ruzstd 0.9.1
published: '2026-10-11'
updated: '2026-10-13'
sourceUpdated: '2026-10-13T10:45:04.080993335Z'
source: OSV
sourceUrl: 'https://osv.dev/vulnerability/RUSTSEC-2026-0344'
references:
  - url: 'https://crates.io/crates/ruzstd'
  - url: 'https://rustsec.org/advisories/RUSTSEC-2026-0344.html'
  - url: >-
      https://github.com/KillingSpark/zstd-rs/commit/d3907c960ca4a1aa44cc38340137c5679dd98f5a
tags:
  - osv
  - rust
ingestedAt: '2026-10-13T11:45:30.201Z'
---

## Overview

A crafted `.zst` input under 128 KB can force `ruzstd` to allocate several gigabytes at once, crashing the process with an out-of-memory condition. Since `ruzstd` is a decoder for untrusted input, a single small file is enough to take down anything decoding it.

The compressed size of a block was capped at 128 KB, but a compressed block's **decompressed** size was never checked against `Block_Maximum_Size = min(Window_Size, 128 KiB)` (RFC 8878). In `execute_sequences` the output was built with no running bound and no flush between blocks, so one block could expand to gigabytes — bypassing both the configured window-size limit and the block-by-block streaming that would otherwise release memory. (A related `u32` counter overflow on such a block caused an additional panic.)

This is a denial of service only; memory access stays in bounds (no corruption, no RCE).

`ruzstd` is also built as a dependency of the Rust standard library via `rustc-dep-of-std`; in the toolchain it is used only to load zstd-compressed debug symbols, so the toolchain-side impact is limited.

**Fixed in 0.9.1** (commit `d3907c9`), which enforces the per-block output bound. Upgrade to `ruzstd >= 0.9.1`.

## Affected packages

- `ruzstd >= 0.0.0-0, < 0.9.1`

## Remediation

Upgrade to a patched release:

- `ruzstd 0.9.1`