russh: Post-decompression SSH packet size was not bounded, allowing remote oversized compressed packets

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

• CVE-2026-46702: 0.27% estimated exploitation activity in the next 30 days; percentile 19.03 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary When SSH compression is enabled, russh accepted compressed packets whose on-wire size passed the normal transport packet-length checks but whose decompressed size was much larger. This allowed a remote peer to send oversized post-decompression packets that should have been rejected. In current releases, this is a remote denial-of-service / resource-exhaustion issue in the post-decompression receive path. In older releases before 0.58.0, the same remote decompression path used CryptoVec, which appears to make the historical impact worse. Details The normal SSH transport read path enforces a packet-length limit before the packet body is read: - russh/src/cipher/mod.rs However, RFC 4253 compression is applied to the SSH payload field only. The packetlength field and MAC are computed over the compressed payload, so a packet that is reasonably sized on the wire can still expand to a much larger message body after decompression. In russh, compressed packet bodies are later…

Published by the source

29 May 2026, 19:37 UTC

Last modified by the source

11 Jun 2026, 14:06 UTC

Source last checked

26 Oct 2026, 15:42 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-wwx6-x28x-8259

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# Patch Next advisory brief: CVE-2026-46702

Advisory: russh: Post-decompression SSH packet size was not bounded, allowing remote oversized compressed packets
IDs: CVE-2026-46702, GHSA-wwx6-x28x-8259
Record: https://patchnext.com/advisories/cve-2026-46702 (revision 1, source checked 26 Oct 2026, 15:42 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: russh 0.61.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- crates.io russh: affected >= 0.34.0, < 0.61.1; fixed in 0.61.1

## Suggested inspection (read-only)
- crates.io russh: 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 russh.
- 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://github.com/advisories/GHSA-wwx6-x28x-8259 (GitHub-reviewed advisory GHSA-wwx6-x28x-8259 lists affected ranges: crates.io russh >=0.34.0 <0.61.1)

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