The Kubernetes Controller Manager must have secure binding.
Limiting the number of attack vectors and implementing authentication and encryption on the endpoints available to external sources is paramount when securing the overall Kubernetes cluster. The Controller Manager API service exposes port 10252/TCP by default for health and metrics information use. This port does not encrypt or authenticate connections. If this port is exposed externally, an attacker can use this port to attack the entire Kubernetes cluster. By setting the bind address to only localhost (i.e., 127.0.0.1), only those internal services that require health and metrics information can access the Control Manager API.