# CVE-2026-111061: russh agent server converts constraint records into unbounded never-rolled-back tasks

> An attacker can exhaust memory and tasks in the russh SSH agent by sending repeated constraint records, causing a denial of service.

- **Severity:** Medium 4.3 (`CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 19 Oct 2026
- **Updated:** 19 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-111061, GHSA-4wc5-f2rc-q74m, UBUNTU-CVE-2026-111061

## What is CVE-2026-111061?

CVE-2026-111061 is a medium-severity denial of service vulnerability in Eugeny russh, published on 19 Oct 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

russh is a Rust SSH client and server library that includes an SSH agent protocol implementation. Prior to 0.64.1, the agent server spawns a separate long-lived task for every SSH_AGENT_CONSTRAIN_LIFETIME record in a constrained add-key request. The loop accepts repeated lifetime records, clones the key blob into each task, and does not roll back tasks when later constraint parsing fails. An attacker that can speak the agent protocol locally or through agent forwarding can exhaust memory and tasks until the agent process is starved or terminated, denying SSH agent service. This issue is fixed in version 0.64.1.

Weakness: CWE-770 (Allocation of Resources Without Limits or Throttling)

## Which versions are affected by CVE-2026-111061?

2 open source packages ship an affected version, including russh.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `russh` | crates.io | All versions | 0.64.1 |
| `russh` | crates.io | All versions | 0.64.1 |

## How do I fix CVE-2026-111061?

Upgrade russh to 0.64.1 or later.

## Is CVE-2026-111061 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-111061 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-111061 and fix it if it is affected.

What it is: CVE-2026-111061 is a medium-severity denial of service vulnerability in Eugeny russh, published on 19 Oct 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-111061 exists.

Affected packages and fixed versions:
- russh (crates.io): affected all versions; fixed in 0.64.1
- russh (crates.io): affected all versions; fixed in 0.64.1

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-2026-111061/ (Markdown: https://insights.sbomify.com/CVE-2026-111061/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-111061
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-111061
- OSV: https://osv.dev/vulnerability/CVE-2026-111061

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-111061/
Summaries are generated and may contain mistakes; the official description above is the record.