# CVE-2026-116774: russh: peer-declared zero maximum packet size permanently stalls channel writes (silent AsyncWrite hang)


- **Severity:** Medium 4.3 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L`)
- **Exploited in the wild:** Not known
- **Fix available:** No
- **Published:** 27 Oct 2026
- **Updated:** 28 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-116774, GHSA-fw5c-8223-6h42, UBUNTU-CVE-2026-116774

## What is CVE-2026-116774?

CVE-2026-116774 is a medium-severity vulnerability in Eugeny russh, published on 27 Oct 2026. 

### Official description

russh is a Rust SSH client and server library that includes an SSH agent protocol implementation. From 0.60.0 until 0.65.0, channel-open parsing accepts a peer-declared maximum_packet_size of zero and passes it into ChannelTx::poll_writable in russh/src/channels/io/tx.rs. The Channel::data, Channel::make_writer, and Channel::into_stream asynchronous write paths then calculate a writable size of zero and remain pending forever because window adjustments cannot satisfy a static zero packet maximum. An authenticated client can strand server writes, and a malicious server can strand client writes, allowing affected tasks, channels, and connections to accumulate without surfacing an error. This issue is fixed in version 0.65.0.

Weakness: CWE-835 (Loop with Unreachable Exit Condition), CWE-400 (Uncontrolled Resource Consumption)

## Which versions are affected by CVE-2026-116774?


## How do I fix CVE-2026-116774?

No fix has been published for CVE-2026-116774 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-116774 being exploited?

There is no known exploitation of CVE-2026-116774 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-116774 and fix it if it is affected.

What it is: CVE-2026-116774 is a medium-severity vulnerability in Eugeny russh, published on 27 Oct 2026. 
Exploitation: There is no known exploitation of CVE-2026-116774 in the wild and no public exploit code.

Affected product: Eugeny russh. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-116774/ (Markdown: https://insights.sbomify.com/CVE-2026-116774/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-116774
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-116774
- OSV: https://osv.dev/vulnerability/CVE-2026-116774

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-116774/
Summaries are generated and may contain mistakes; the official description above is the record.