Title

The SSH client must not permit tunnels. (Cat II impact)

Discussion

OpenSSH has the ability to create network tunnels (layer-2 and layer-3) over an SSH connection. 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

Check the SSH client configuration for the Tunnel setting. # grep -i Tunnel /etc/ssh/ssh_config | grep -v '^#' If the setting is not present, or not set to no, this is a finding.

Fix Text

Edit the SSH client configuration and add or edit the Tunnel setting value to no.

Additional Identifiers

Rule ID: SV-26775r1_rule

Vulnerability ID: V-22481

Group Title: GEN005532

Expert Comments

CCIs tied to check.

Controls tied to check. These are derived from the CCIs shown above.