russh kex_done: shared-secret callback runs before server host-key verification

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-128087
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-11-13 19:19:31 UTC
Updated2026-11-13 19:19:31 UTC
Descriptionrussh 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.

Risk And Classification

Primary CVSS: v3.1 3.7 LOW from [email protected]

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

Problem Types: CWE-696 | CWE-863 | CWE-696 CWE-696: Incorrect Behavior Order | CWE-863 CWE-863: Incorrect Authorization

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary3.7LOWCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
3.1CNADECLARED3.7LOWCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
None
Availability
None

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Eugeny Russh affected >= 0.55.0, < 0.65.1 Not specified

References

ReferenceSourceLinkTags
github.com/Eugeny/russh/pull/808 [email protected] github.com
github.com/Eugeny/russh/releases/tag/v0.65.1 [email protected] github.com
github.com/Eugeny/russh/security/advisories/GHSA-9264-jvgf-6w2f [email protected] github.com
github.com/Eugeny/russh/commit/43a46d67a80a7355fcd2fb25e7e00d79aec8184c [email protected] github.com
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