vulnerability / NVI-00018654 / Revision 1
russh server userauth state is not reset when authentication principal changes
GitHub lists this reviewed advisory for russh. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.
This report has not inspected your inventory, configuration, deployed build, reachability or evidence. A catalog listing and a severity score do not establish exposure or compromise.
01 / Meaning
Why it matters
Published affected context helps an owner decide what evidence to gather. This report has not examined your application.
5.3 medium
GitHub source severity; exploitability and local consequence require separate evidence.
As of · GitHub Advisory Database
02 / Applicability
The affected context
Affected versions, configuration prerequisites and known exclusions are public. Confirm each one against the deployed service.
russh
source listed>= 0.34.0-beta.1, < 0.61.0
### Summary 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. Applications are responsible for any authentication state they keep in their own handlers, but russh must reset or separate state that russh itself owns. ### Details The relevant server-side auth logic is in: - `russh/src/server/encrypted.rs` - `russh/src/auth.rs` RFC 4252 section 5 says the `user name` and `service name` fields are repeated in every `SSH_MSG_USERAUTH_REQUEST` and may change. It also says the server implementation must check those fields in every message and flush accumulated authentication state if they change; if it cannot flush that state, it
03 / Response
What to do next
- investigate
Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.
Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. GitHub Advisory Database
A fixed release is not deployment evidence.
Check current vendor support and compatibility. After making a change, verify the deployed build and relevant runtime conditions. Keep the evidence, owner and time. An updated lockfile alone does not prove what is running.
04 / Limits
What this report cannot establish
- Customer inventory, deployment, reachability and exploitation have not been inspected.
05 / Provenance
Sources you can inspect
Each assertion retains its source. Mirrored records may repeat one underlying publisher; additional links are not independent corroboration.
- GHSA-hpv4-5h6f-wqr3 ↗
GitHub Advisory Database · vendor advisory
Observed . GitHub Advisory Database; CC-BY-4.0. Each advisory links its original attribution. Null normalizes fields.
Public revision history
Only published revisions appear here. Routine fetches do not create a material-change event.
- Revision 1 ·
First indexed by Null; source disclosure date is shown separately.