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:

# esxcli system ssh server config list -k permittunnel

or

From a PowerCLI command prompt while connected to the ESXi host, run the following commands:

$esxcli = Get-EsxCli -v2 $esxcli.system.ssh.server.config.list.invoke() | Where-Object {$_.Key -eq 'permittunnel'}

Example result:

permittunnel no

If "permittunnel" is not configured to "no", this is a finding.

From an ESXi shell, run the following command:

# esxcli system ssh server config set -k permittunnel -v no

or

From a PowerCLI command prompt while connected to the ESXi host, run the following commands:

$esxcli = Get-EsxCli -v2 $arguments = $esxcli.system.ssh.server.config.set.CreateArgs() $arguments.keyword = 'permittunnel' $arguments.value = 'no' $esxcli.system.ssh.server.config.set.Invoke($arguments)