# russh: peer-declared zero maximum packet size permanently stalls channel writes (silent AsyncWrite hang)

Advisory record · `GHSA-fw5c-8223-6h42`

- **Identifiers:** `GHSA-fw5c-8223-6h42` · `CVE-2026-116774`
- **State:** Confirmed
- **Severity:** CVSS 4.3 Medium
- **Critical:** No
- **Weakness (CWE):** [CWE-400](https://cwe.mitre.org/data/definitions/400.html) · [CWE-835](https://cwe.mitre.org/data/definitions/835.html)
- **Tags:** [Denial of service](https://agentprime.io/advisories/tag/dos.md)
- **Published:** 30 Oct 2026
- **Updated:** 30 Oct 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 30 Oct 2026, 22:58 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `russh` (crates.io): affected `>=0.60.0, <0.65`; fixed in `0.65`

## Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

> russh versions 0.60.0 up to but not including 0.65 accept a peer's channel maximum packet size of 0 without checking it. A connected peer that sends this value can make writes on that channel through the AsyncWrite path, such as Channel::data() or into_stream(), hang forever without returning an error. Upgrade to russh 0.65, the fixed version.

Written 3 Nov 2026.

## Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

## Severity and exploitation

- 4.3 Medium, CVSS 3.1: `CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L`, from CNA (GitHub_M)

- **CISA KEV:** Not listed.
- **EPSS:** 0.0026, the 17th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

- 31 Oct 2026, 14:24 UTC: First seen by agentprime
- 31 Oct 2026, 14:24 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-fw5c-8223-6h42)

## Sources

- [GitHub Advisory Database: GHSA-fw5c-8223-6h42](https://github.com/advisories/GHSA-fw5c-8223-6h42)
- [OSV: GHSA-fw5c-8223-6h42](https://osv.dev/vulnerability/GHSA-fw5c-8223-6h42)
- <https://github.com/Eugeny/russh/security/advisories/GHSA-fw5c-8223-6h42>
- <https://nvd.nist.gov/vuln/detail/CVE-2026-116774>
- <https://github.com/Eugeny/russh/commit/39cb9dbaa37caf555d34c6c22efa3bbbff9e186c>
- <https://github.com/Eugeny/russh>
- <https://github.com/Eugeny/russh/releases/tag/v0.65.0>

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.

## Check whether this affects you

A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/GHSA-fw5c-8223-6h42>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

---

The web page: <https://agentprime.io/advisories/GHSA-fw5c-8223-6h42/>. Everything for agents: <https://agentprime.io/llms.txt>.