RUSTSEC-2026-0344

Vulnerability from osv_rustsec – Published: 2026-10-11 12:00 – Updated: 2026-10-13 10:39 – Source website
VLAI
Summary
Decompression bomb in `ruzstd`: a tiny input can exhaust memory (OOM)
Details

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.

Severity
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
References
To clipboard 

{
  "affected": [
    {
      "database_specific": {
        "categories": [
          "denial-of-service"
        ],
        "cvss": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
        "informational": null
      },
      "ecosystem_specific": {
        "affected_functions": null,
        "affects": {
          "arch": [],
          "functions": [],
          "os": []
        }
      },
      "package": {
        "ecosystem": "crates.io",
        "name": "ruzstd",
        "purl": "pkg:cargo/ruzstd"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0.0.0-0"
            },
            {
              "fixed": "0.9.1"
            }
          ],
          "type": "SEMVER"
        }
      ],
      "versions": []
    }
  ],
  "aliases": [],
  "database_specific": {
    "license": "CC0-1.0"
  },
  "details": "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.\n\nThe compressed size of a block was capped at 128 KB, but a compressed block\u0027s **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 \u2014 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.)\n\nThis is a denial of service only; memory access stays in bounds (no corruption, no RCE).\n\n`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.\n\n**Fixed in 0.9.1** (commit `d3907c9`), which enforces the per-block output bound. Upgrade to `ruzstd \u003e= 0.9.1`.",
  "id": "RUSTSEC-2026-0344",
  "modified": "2026-10-13T10:39:39Z",
  "published": "2026-10-11T12:00:00Z",
  "references": [
    {
      "type": "PACKAGE",
      "url": "https://crates.io/crates/ruzstd"
    },
    {
      "type": "ADVISORY",
      "url": "https://rustsec.org/advisories/RUSTSEC-2026-0344.html"
    },
    {
      "type": "WEB",
      "url": "https://github.com/KillingSpark/zstd-rs/commit/d3907c960ca4a1aa44cc38340137c5679dd98f5a"
    }
  ],
  "related": [],
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Decompression bomb in `ruzstd`: a tiny input can exhaust memory (OOM)"
}



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