Title

The Kubernetes Controller Manager must have secure binding. (Cat II impact)

Discussion

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.

Check Content

Ensure bind-address is set correctly. Run this command on the RKE2 Control Plane: /bin/ps -ef | grep kube-controller-manager | grep -v grep If --bind-address is not set to "127.0.0.1" or is not configured, this is a finding.

Fix Text

Edit the RKE2 Configuration File /etc/rancher/rke2/config.yaml on the RKE2 Control Plane and set the following "kube-controller-manager-arg" argument: - bind-address=127.0.0.1 Once the configuration file is updated, restart the RKE2 Server. Run the command: systemctl restart rke2-server

Additional Identifiers

Rule ID: SV-254556r960792_rule

Vulnerability ID: V-254556

Group Title: SRG-APP-000033-CTR-000090

Expert Comments

CCIs tied to check.

Controls tied to check. These are derived from the CCIs shown above.