Auth bypass in Eugeny Russh
CVE-2026-46705
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.
Vulnerability class: Broken Authentication
Published · last modified .
CVSS v3 metric
CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N.
EPSS exploit prediction
EPSS: 0.002 (12.3th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 12th percentile — 12.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.002 · change: -0.001
Affected products
- Eugeny Russh — versions >= 0.34.0-beta.1, < 0.61.0
Weakness classification (CWE)
References
Frequently asked questions
- What is CVE-2026-46705?
- CVE-2026-46705 is a medium-severity vulnerability in Eugeny Russh, classified under Improper Authentication. CVSS score: 5.3/10. Published 2026-06-10.
- How severe is CVE-2026-46705?
- Medium severity. CVSS v3 base score is 5.3 out of 10.