---
id: "CVE-2026-116774"
kind: "vulnerability"
aliases: ["CVE-2026-116774"]
title: "russh: zero maximum packet size strands SSH channel writes forever"
severity: "medium"
cvss: 4.3
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["package", "russh", "rust", "self-hosted", "ssh"]
not_affected_if: ["russh-0.65.0-or-later", "russh-below-0.60.0"]
published_at: "2026-10-27T21:18:05+00:00"
first_seen_at: "2026-10-27T21:29:21+00:00"
updated_at: "2026-10-27T21:30:22+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-116774", "first_seen_at": "2026-10-27T21:29:21+00:00"}]
---

# russh: zero maximum packet size strands SSH channel writes forever

russh, a Rust SSH client and server library, accepts a zero maximum_packet_size when a channel opens, from version 0.60.0 through 0.65.0. Channel writes then wait forever, so an authenticated peer or a malicious server can pile up stuck tasks and connections without any error.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Run `cargo tree -i russh` in the project to find the russh version in use
- Check Cargo.lock for a `russh` entry between `0.60.0` and `0.64.x`

## Fix

- Upgrade the russh crate to `0.65.0` or later with `cargo update -p russh`

## Timeline

- 2026-10-27T21:29:21+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-116774

## From the sources

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.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_