Decompression bomb in ruzstd: a tiny input can exhaust memory (OOM)

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.5 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

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…

Published by the source

11 Oct 2026, 12:00 UTC

Last modified by the source

13 Oct 2026, 10:45 UTC

Source last checked

23 Oct 2026, 22:04 UTC

1. Revision 1 · created · 24 Oct 2026

   Published from osv record RUSTSEC-2026-0344

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# Patch Next advisory brief: rustsec-2026-0344

Advisory: Decompression bomb in `ruzstd`: a tiny input can exhaust memory (OOM)
IDs: rustsec-2026-0344
Record: https://patchnext.com/advisories/rustsec-2026-0344 (revision 1, source checked 23 Oct 2026, 22:04 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: ruzstd 0.9.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- crates.io ruzstd: affected >= 0.0.0-0, < 0.9.1; fixed in 0.9.1

## Suggested inspection (read-only)
- crates.io ruzstd: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on ruzstd.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/RUSTSEC-2026-0344 (OSV record RUSTSEC-2026-0344 lists affected ranges: crates.io ruzstd >=0.0.0-0 <0.9.1 (fixed))

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