The SSH daemon must not permit tunnels.

From VMware vSphere ESXi 6.0 Security Technical Implementation Guide

Part of SRG-OS-000480-VMM-002000

Associated with: CCI-000366

SV-77709r1_rule The SSH daemon must not permit tunnels.

Vulnerability 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

To verify the PermitTunnel setting, run the following command: # grep -i "^PermitTunnel" /etc/ssh/sshd_config If there is no output or the output is not exactly "PermitTunnel no", this is a finding.

Fix text

To set the PermitTunnel setting, add or correct the following line in "/etc/ssh/sshd_config": PermitTunnel no

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