CVE-2023-46445

What it actually does

Man-in-the-middle attacker can inject or alter the SSH extension information message during initial handshake per RFC 8308, bypassing intended negotiation and potentially enabling integrity violations in session parameters.

Why it matters to the business

Environments relying on AsyncSSH for secure remote access face risk of session tampering or unauthorized control when an attacker has network interception capability, though low exploit probability limits widespread operational disruption.

How an attack unfolds

Attacker intercepts network traffic between SSH client and server, modifies the extension info message during the RFC 8308 negotiation phase of the handshake to influence session behavior without triggering standard authentication checks.

How to fix it

Upgrade ronf/asyncssh to version 2.14.1 or later by applying the fix from commit 0d6de9aec1a81a4f6ff7400c24b699eb6137fba3; verify all deployments pull from the corrected source.

How to confirm the fix worked

Confirm installed package version meets or exceeds 2.14.1 and review release notes for the rogue extension negotiation patch; perform functional tests of SSH connections to ensure negotiation behaves as expected.

Typical attack path

1. Establish man-in-the-middle position on the network path between client and server
2. Intercept the initial SSH protocol handshake packets
3. Alter or inject the extension information message
4. Allow the modified negotiation to complete and proceed with the session

How to detect it

Review SSH client and server logs for anomalous extension negotiation messages or unexpected RFC 8308 parameters; correlate with network flow data indicating possible interception attempts.

What your security team should do

• Prioritize upgrade of all AsyncSSH instances to the fixed release
• Implement network controls that reduce man-in-the-middle exposure such as certificate pinning or VPN enforcement
• Audit dependency graphs for downstream packages that embed vulnerable AsyncSSH versions