CVE-2026-128088Eugeny russh time-of-check to time-of-use race
CVE-2026-128088 is a time-of-check to time-of-use race in Eugeny russh, rated low (2.2 on CVSS 3.1).
Why this priority: Low severity, with no exploitation signal.
Published · Updated · NVD status: Deferred
What it is
Something is checked, then changed by an attacker before it is used. A permission check exists but gets the answer wrong for some callers.
How it is reached
An attacker can exploit it by someone who can already run code or sign in on the machine, with an ordinary user account, but someone has to act first, such as opening a file or following a link. Success also depends on conditions the attacker does not fully control.
What an attacker gains
The direct impact is limited: partial access to data or a partial outage. In practice, this kind of flaw lets an attacker win a timing window to bypass a check or corrupt shared state.
Is it being exploited?
There is no public report of exploitation yet.
What to do
- Upgrade Eugeny russh to 0.65.1 or later.
- Limit who can run code or sign in on the hosts that run it.
- Warn the people who use it, and filter files and links on the way in.
Description from NVD
russh is a Rust SSH client and server library that includes an SSH agent protocol implementation. Prior to version 0.65.1, try_sign() captures an Arc<PrivateKey> before awaiting Agent::confirm() and does not revalidate the shared lock state or key presence after the await. This is a distinct residual defect in the remediation for CVE-2026-116794. A peer, including a remote SSH server using agent forwarding, can begin a confirmation-constrained signature request while the agent is unlocked and receive the signature after another connection locks the agent if the stale confirmation returns true. New post-lock requests are rejected and private key material is not disclosed, but the pending operation bypasses the current lock state. This issue is fixed in version 0.65.1.
What this means for your architecture.
A CVE names a product. Whether it matters depends on where that product sits in your systems: what reaches it, which trust boundary it guards and what it can reach once compromised. Veriom maps your components, their relationships and your trust boundaries from your code, cloud and delivery evidence, so you can see where a component like this sits. The radar itself does not look at your systems.
Components it touches
- Request handlers and jobs that share state. The flaw sits between concurrent requests or processes.
- Permission checks in APIs and admin surfaces. The flaw sits between one role or tenant and another.
- Multi-tenant services. The flaw sits between one role or tenant and another.
Trust boundaries in play
- Host boundary. The attacker needs a foothold on the machine first; the flaw turns a small foothold into a bigger one.
- People who open files and links. Mail, chat and browsers are the delivery path.
- Between concurrent requests or processes. An attacker who crosses it can win a timing window to bypass a check or corrupt shared state.
- Between one role or tenant and another. An attacker who crosses it can reach data or actions their role should not allow.
Questions to answer about your own systems
- Where does Eugeny russh run in your systems, and at which version?
- Which of those hosts also run code or users you do not fully trust?
- What can it reach once compromised: which data stores, secrets and services?
Sources
- CVE records and CVSS scores from the NVD CVE API. This product uses the NVD API but is not endorsed or certified by the NVD.
- Exploitation status from CISA’s Known Exploited Vulnerabilities catalog.
- Exploit likelihood from FIRST’s Exploit Prediction Scoring System (EPSS), refreshed daily.
- Explanations are written by Veriom from fixed templates over each record’s data, not by a person reviewing each CVE. Descriptions are quoted from the records as published.