The ESXi host Secure Shell (SSH) daemon must be configured to not allow gateway ports.

SSH Transmission Control Protocol (TCP) connection forwarding provides a mechanism to establish TCP connections proxied by the SSH server. This function can provide convenience similar to a virtual private network (VPN) with the similar risk of providing a path to circumvent firewalls and network Access Control Lists (ACLs). Gateway ports allow remote forwarded ports to bind to nonloopback addresses on the server.

From an ESXi shell, run the following command:

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

Expected result:

gatewayports 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":

GatewayPorts no