AIKIDO-2026-918588
russh is vulnerable to Improper Restriction of Excessive Authentication Attempts
37
Low Risk
This Affects:
russhTL;DR
The russh SSH server does not enforce the configured max_auth_attempts limit in the USERAUTH_REQUEST runtime path. The per-connection attempt counter is incremented but never compared against the configured cap, so a remote unauthenticated client can keep sending authentication requests on a single connection beyond the limit operators expect. This expands the online password-guessing window and increases authentication backend workload where deployers rely on this control. The fix enforces the cap in the auth-request branch and disconnects the client once the threshold is reached.
Who does this affect?
You are affected if you are using a version that falls within the vulnerable range, you run the russh server and rely on Config.max_auth_attempts to cap authentication attempts.
Background info
russh is vulnerable to Improper Restriction of Excessive Authentication Attempts in versions 0.0.1 - 0.62.5.
How to fix this
Upgrade the russh library to the patch version.
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