Vulnerability · Published Oct 19, 2026 · Assigned by GitHub_M
CVE-2026-111061russh agent server converts constraint records into unbounded never-rolled-back tasks
Medium 4.3
In plain English
A medium-severity resource allocation without limits in russh from Eugeny. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 28% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:14 | rust-russh | 0.64.1-1 | DEBIAN-CVE-2026-111061 |
| Ubuntu:26.10 | rust-russh | no fix listed | UBUNTU-CVE-2026-111061 |
Affected products (as reported)
Weakness: CWE-770 · Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
References
- https://github.com/Eugeny/russh/security/advisories/GHSA-4wc5-f2rc-q74m x_refsource_CONFIRM
- https://github.com/Eugeny/russh/commit/4c305033d72f8e5dd21a3fd4c53a6c291a16ebd1 x_refsource_MISC
- https://github.com/Eugeny/russh/releases/tag/v0.64.1 x_refsource_MISC