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Kubernetes must have a Pod Security Admission control file configured.


Finding ID Version Rule ID IA Controls Severity
V-254800 CNTR-K8-002011 SV-254800r864040_rule High
An admission controller intercepts and processes requests to the Kubernetes API prior to persistence of the object, but after the request is authenticated and authorized. Kubernetes (> v1.23)offers a built-in Pod Security admission controller to enforce the Pod Security Standards. Pod security restrictions are applied at the namespace level when pods are created. The Kubernetes Pod Security Standards define different isolation levels for Pods. These standards let you define how you want to restrict the behavior of pods in a clear, consistent fashion.
Kubernetes Security Technical Implementation Guide 2022-12-02


Check Text ( C-58411r863727_chk )
Change to the /etc/kubernetes/manifests directory on the Kubernetes Control Plane. Run the command:

"grep -i admission-control-config-file *"

If the setting "admission-control-config-file" is not configured in the Kubernetes API Server manifest file, this is a finding.

Inspect the .yaml file defined by the --admission-control-config-file. Verify PodSecurity is properly configured.
If least privilege is not represented, this is a finding.
Fix Text (F-58357r863728_fix)
Modify the file /etc/kubernetes/manifests/kube-apiserver.yaml and add the flag --admission-control-config-file (with a valid path for the file) to the apiserver configuration.

Create an admission controller config file:
Example File:
apiVersion: apiserver.config.k8s.io/v1
kind: AdmissionConfiguration
- name: PodSecurity
apiVersion: pod-security.admission.config.k8s.io/v1beta1
kind: PodSecurityConfiguration
# Defaults applied when a mode label is not set.
enforce: "privileged"
enforce-version: "latest"
# Don't forget to exempt namespaces or users that are responsible for deploying
# cluster components, because they need to run privileged containers
usernames: ["admin"]
namespaces: ["kube-system"]

See For More Details:
Migrate from PSP to PSA:

Best Practice: https://kubernetes.io/docs/concepts/security/pod-security-policy/#recommended-practice