The SSH client must be configured to only use the SSHv2 protocol.

From VMware ESXi Server 5.0 Security Technical Implementation Guide

Associated with: CCI-000366

SV-51272r2_rule The SSH client must be configured to only use the SSHv2 protocol.

Vulnerability discussion

SSHv1 is not a DoD-approved protocol and has many well-known vulnerability exploits. Exploits of the SSH client could provide access to the system with the privileges of the user running the client.

Check content

Disable lock down mode. Enable the ESXi Shell. Check the SSH client configuration for required protocol. # grep -i "Protocol 2" /etc/ssh/ssh_config | grep -v '^#' Re-enable lock down mode. If the returned protocol list contains anything except 2, this is a finding. If the /etc/ssh/ssh_config file does not exist or the Protocol option is not set, this is not a finding because the SSH client cannot enforce the Protocol setting on a compliant SSH server.

Fix text

Disable lock down mode. Enable the ESXi Shell. Edit the SSH client configuration and add/modify the "Protocol" configuration for Protocol 2 only. # vi /etc/ssh/ssh_config Re-enable lock down mode.

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