---
id: "CVE-2026-116696"
kind: "vulnerability"
aliases: ["CVE-2026-116696"]
title: "russh: SSH agent accepts unlimited confirm constraints, growing memory"
severity: "low"
cvss: 3.3
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["package", "russh", "rust", "self-hosted", "ssh"]
not_affected_if: ["client-only", "no-agent-server"]
published_at: "2026-10-27T21:18:05+00:00"
first_seen_at: "2026-10-27T21:29:21+00:00"
updated_at: "2026-10-27T21:30:24+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-116696", "first_seen_at": "2026-10-27T21:29:21+00:00"}]
---

# russh: SSH agent accepts unlimited confirm constraints, growing memory

The russh Rust SSH library's agent server appends every SSH_AGENT_CONSTRAIN_CONFIRM record when adding a key, with no count or size limit. A client that can reach the agent socket, including a forwarded agent session, can grow the process's memory until it runs out.

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

## How to check

- Check the russh version in `Cargo.lock` for `russh` below `0.65.0`
- Check whether the application runs `russh::keys::agent::server::serve`, which is the vulnerable agent server

## Fix

- Upgrade `russh` to `0.65.0` or later

## Timeline

- 2026-10-27T21:29:21+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-116696

## From the sources

russh is a Rust SSH client and server library that includes an SSH agent protocol implementation. Prior to 0.65.0, russh::keys::agent::server::serve in russh/src/keys/agent/server.rs accepts repeated SSH_AGENT_CONSTRAIN_CONFIRM records while adding a key and appends every Constraint::Confirm record to the key's retained constraint vector without a count or memory limit. A process that can connect to the agent socket, including the remote side of a forwarded agent session, can repeatedly add constrained keys and cause renewable memory growth that persists for the process lifetime because keys without a lifetime constraint do not expire. 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_