russh try_sign: asynchronous confirmation can sign after agent lock

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

2.2 · CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:U/C:N/I:L/A:N

EPSS

• CVE-2026-128088: 0.11% estimated exploitation activity in the next 30 days; percentile 1.45 (FIRST EPSS, 2026-11-14). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary In russh `0.65.0`, a sign request for a confirmation-constrained key can retain and use the private key after another connection locks the agent. `try_sign()` snapshots an `Arc ` before awaiting `Agent::confirm()` and does not revalidate the shared lock state after the await. An agent-forwarding peer can therefore obtain a signature while the agent is locked and every new request is being rejected.

Details The agent's lock and key stores are shared by all connections. `respond()` reads the lock state once, then dispatches a sign request: ```rust let is_locked = { // ... read the shared lock ... }; // ... Some((&13, mut r)) if !is_locked && agentref.confirm_request(MessageType::Sign).await => { let agent = self.agent.take().ok_or(Error::AgentFailure)?; let (agent, signed) = self.try_sign(agent, &mut r, writebuf).await?; ``` In `try_sign()`, russh clones the private key from the shared store and drops the store lock before awaiting the asynchronous confirmation…

Published by the source

13 Nov 2026, 19:10 UTC

Last modified by the source

13 Nov 2026, 19:15 UTC

Source last checked

14 Nov 2026, 08:25 UTC

1. Revision 2 · amended · 14 Nov 2026

   Amended from osv record GHSA-736f-c93q-9fwx

2. Revision 1 · created · 13 Nov 2026

   Published from ghsa record GHSA-736f-c93q-9fwx

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# Patch Next advisory brief: CVE-2026-128088

Advisory: russh try_sign: asynchronous confirmation can sign after agent lock
IDs: CVE-2026-128088, GHSA-736f-c93q-9fwx
Record: https://patchnext.com/advisories/cve-2026-128088 (revision 2, source checked 14 Nov 2026, 08:25 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Low (CVSS 2.2)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: russh 0.65.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- crates.io russh: affected >= 0.65.0, < 0.65.1; fixed in 0.65.1

## Suggested inspection (read-only)
- crates.io russh: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on russh.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-736f-c93q-9fwx (GitHub-reviewed advisory GHSA-736f-c93q-9fwx lists affected ranges: crates.io russh >=0.65.0 <=0.65.0)
- Verified: https://osv.dev/vulnerability/GHSA-736f-c93q-9fwx (OSV record GHSA-736f-c93q-9fwx lists affected ranges: crates.io russh >=0.65.0 <0.65.1 (fixed))

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