russh has pre-auth DoS via unbounded allocation in its keyboard-interactive auth handler — CVE-2026-42189

Summary

## Summary A pre-authentication denial-of-service vulnerability exists in the server's keyboard-interactive authentication handler. A malicious client can crash any russh-based server that implements keyboard-interactive auth (e.g., for 2FA/TOTP) with a single malformed packet, requiring no credentials. ## Vulnerability Details In `russh/src/server/encrypted.rs`, the function `read_userauth_info_response` decodes a…

Product

rust: russh

What to do

General, cautious steps (verify details in the official source):

• Prioritize patching or mitigation immediately (treat as actively risky).
• Identify affected product versions in your inventory and verify whether you are impacted.
• Apply vendor patches/updates or recommended mitigations as soon as available.
• Read the official advisory for exact affected versions and remediation steps.

Official advisory

• Read the official source
• CVE Record
• NVD

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