The SSH client must be configured to not allow TCP forwarding.

From VMware ESXi Server 5.0 Security Technical Implementation Guide

Associated with: CCI-000366

SV-51065r3_rule The SSH client must be configured to not allow TCP forwarding.

Vulnerability discussion

SSH TCP connection forwarding provides a mechanism to establish TCP connections proxied by the SSH server. This function can provide similar convenience to a Virtual Private Network (VPN) with the similar risk of providing a path to circumvent firewalls and network ACLs.

Check content

Disable lock down mode. Enable the ESXi Shell. Execute the following command(s): # grep Forward /etc/ssh/ssh_config Re-enable lock down mode. If any of the following attributes (ForwardAgent, ForwardX11, or ForwardX11Trusted) exist and are not set to "no", this is a finding. If the /etc/ssh/ssh_config file does not exist, this is not a finding.

Fix text

Disable lock down mode. Enable the ESXi Shell. Execute the following command(s): # vi /etc/ssh/ssh_config Add/modify the attribute line entry to the following (quotes for emphasis only): "ForwardAgent no" "ForwardX11 no" "ForwardX11Trusted no" Re-enable lock down mode.

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