CVE-2026-46705 russh server userauth state is not reset when authentication principal changes
Attackers can bypass authentication checks in russh SSH servers by exploiting state persistence when changing user or service names during login.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-46705?
CVE-2026-46705 is a medium-severity authentication bypass vulnerability in Eugeny russh, published on 10 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Russh is a Rust SSH client & server library. From version 0.34.0-beta.1 to before version 0.61.0, the russh server authentication path keeps internal userauth state across SSH_MSG_USERAUTH_REQUEST messages without separating that state when the request principal changes. RFC 4252 allows the user name and service name fields to change between authentication requests. The issue is not that such changes are invalid. The issue is that russh-owned authentication state, such as remaining methods, partial-success state, and in-progress method state, can remain associated with the connection and then influence a later request for a different (user, service). This is an internal library state mismatch. This issue has been patched in version 0.61.0.
Weakness: CWE-287
Which versions are affected by CVE-2026-46705?
2 open source packages ship an affected version, including russh.
| Package | Affected | Fixed in |
|---|---|---|
russh crates.io | From 0.34.0-beta.1 | 0.61.0 |
russh crates.io | From 0.34.0-beta.1 | 0.61.0 |
How do I fix CVE-2026-46705?
Upgrade russh to 0.61.0 or later.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-46705 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-46705 exists.
Sources
Also known as DEBIAN-CVE-2026-46705, GHSA-hpv4-5h6f-wqr3.