Ensure that the --bind-address argument is set to 127.0.0.1

Description:

Do not bind the Controller Manager service to non-loopback insecure addresses.

Rationale:

The Controller Manager API service which runs on port 10252/TCP by default is used for health and metrics information and is available without authentication or encryption. As such it should only be bound to a localhost interface, to minimize the cluster's attack surface.

Edit the Controller Manager pod specification file '/etc/kubernetes/manifests/kube-controller-manager.yaml' on the master node and ensure the correct value for the '--bind-address' parameter.