Enable Kubelet authentication using certificates. Rationale: The connections from the apiserver to the kubelet are used for fetching logs for pods, attaching (through kubectl) to running pods, and using the kubelet's port-forwarding functionality. These connections terminate at the kubelet's HTTPS endpoint. By default, the apiserver does not verify the kubelet's serving certificate, which makes the connection subject to man-in-the-middle attacks, and unsafe to run over untrusted and/or public networks. Enabling Kubelet certificate authentication ensures that the apiserver could authenticate the Kubelet before submitting any requests.
Solution
If using a Kubelet config file, edit the file to set authentication: x509: clientCAFile to the location of the client CA file. If using command line arguments, edit the kubelet service file /etc/systemd/system/kubelet.service.d/10-kubeadm.conf on each worker node and set the below parameter in KUBELET_AUTHZ_ARGS variable. --client-ca-file=<path/to/client-ca-file> Based on your system, restart the kubelet service. For example: systemctl daemon-reload systemctl restart kubelet.service Impact: You require TLS to be configured on apiserver as well as kubelets. Default Value: See the GKE documentation for the default value.