Vulnerability Discussion

PodSecurity admission controller is a component that validates and enforces security policies for pods running within a Kubernetes cluster. It is responsible for evaluating the security context and configuration of pods against defined policies.

To enable PodSecurity admission controller on Static Pods (kube-apiserver, kube-controller-manager, or kube-schedule), the argument "--feature-gates=PodSecurity=true" must be set.

To enable PodSecurity admission controller on Kubelets, the featureGates PodSecurity=true argument must be set.

(Note: The PodSecurity feature gate is GA as of v1.25.)

Check

On the Control Plane, change to the manifests' directory at /etc/kubernetes/manifests and run the command:
grep -i feature-gates *

For each manifest file, if the "--feature-gates" setting does not exist, does not contain the "--PodSecurity" flag, or sets the flag to "false", this is a finding.

On each Control Plane and Worker Node, run the command:
ps -ef | grep kubelet

If the "--feature-gates" option exists, this is a finding.

Note the path to the config file (identified by --config).

Inspect the content of the config file:
If the "featureGates" setting is not present, does not contain the "PodSecurity" flag, or sets the flag to "false", this is a finding.

Fix

On the Control Plane, change to the manifests' directory at /etc/kubernetes/manifests and run the command:
grep -i feature-gates *

Ensure the argument "--feature-gates=PodSecurity=true" is present in each manifest file.

On each Control Plane and Worker Node, run the command:
ps -ef | grep kubelet

Remove the "--feature-gates" option if present.

Note the path to the config file (identified by --config).

Edit the Kubernetes Kubelet config file:
Add a "featureGates" setting if one does not yet exist. Add the feature gate "PodSecurity=true".

Restart the kubelet service using the following command:
systemctl daemon-reload && systemctl restart kubelet