CVE-2026-128087
russh kex_done: shared-secret callback runs before server host-key verification
- Low 3.7
Description
russh is a Rust SSH client and server library that includes an SSH agent protocol implementation. From version 0.55.0 until version 0.65.1, the initial key exchange invokes client::Handler::kex_done() with the raw shared secret before check_server_key() accepts the server host key or certificate. A malicious SSH server can therefore trigger application-defined secondary-channel initialization or early data handling even when the server identity is subsequently rejected. Ordinary clients that keep the callback's no-op default or independently defer callback-derived actions until trust is confirmed are not affected. This issue is fixed in version 0.65.1.
Key facts
- Published
- 13 Nov 2026
- Last changed
- 13 Nov 2026
- Assigned by
- GitHub_M
- EPSS
- 0.239% likely to be exploited in the next 30 days, higher than 15.032% of CVEs (scores for 15 Nov 2026)
- SSVC (CISA)
- Exploitation: poc; Automatable: no; Technical impact: partial
Severity scores
Each score is shown as its source gave it. They are not averaged or merged.
- 3.7CVSS 3.1, Lowfrom the CNA (GitHub_M)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
Historical context and remediation
This reference retains the original CVE publication date. A recent record update does not mean a new attack occurred.
No separately sourced impact summary is available on this page yet. Consult the description, version data and dated exploitation evidence.
No explicit remediation statement is available on this page yet. Consult the original record and vendor references before choosing a fix.
Version statuses below come from the CNA. An “unaffected” version is not necessarily a currently supported release or proof of a patch date. EPSS is a dated risk estimate, not a count of historical attacks.
Affected products
| Vendor | Product | Versions |
|---|---|---|
| Eugeny | russh |
|
Timeline
- 13 Nov 2026 Published