The ESXi host Secure Shell (SSH) daemon must not permit tunnels.

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 Access Control Lists (ACLs).

From an ESXi shell, run the following command:

# /usr/lib/vmware/openssh/bin/sshd -T|grep permittunnel

Expected result:

permittunnel no

If the output does not match the expected result, this is a finding.

From an ESXi shell, add or correct the following line in "/etc/ssh/sshd_config":

PermitTunnel no