Cis Oke V180 4.3.1

4.3.1 Ensure latest CNI version is used (Automated)

Profile Applicability

• Level 1

Description

There are a variety of CNI plugins available for Kubernetes. If the CNI in use does not support Network Policies it may not be possible to effectively restrict traffic in the cluster.

Rationale

Kubernetes network policies are enforced by the CNI plugin in use. As such it is important to ensure that the CNI plugin supports both Ingress and Egress network policies.

Impact

None.

Audit

Review the documentation of CNI plugin in use by the cluster, and confirm that it supports network policies.

Check the DaemonSets in the kube-system namespace: Many CNI plugins operate as DaemonSets within the kube-system namespace. To see what's running:

kubectl get daemonsets -n kube-system

Look for known CNI providers like Calico, Flannel, Cilium, etc.

You can further inspect the configuration of these DaemonSets to understand more about the CNI setup:

kubectl get daemonsets -n kube-system -o json \
| jq -r '
  .items[]
  | select(
      (.metadata.name | test("cni|calico|flannel|weave|cilium|canal|multus"; "i"))
      or
      ([.spec.template.spec.containers[].image] | join(" ") | test("cni|calico|flannel|weave|cilium|canal|multus"; "i"))
    )
  | "\(.metadata.name)\timage=\(.spec.template.spec.containers[].image)"
'

Check the CNI Configuration Files: If you have access to the nodes (via SSH), you can check the CNI configuration directly in /etc/cni/net.d/. This often requires node-level access, which might not be available depending on your permissions and the security setup of your environment.

Remediation

As with RBAC policies, network policies should adhere to the policy of least privileged access. Start by creating a deny all policy that restricts all inbound and outbound traffic from a namespace or create a global policy using Calico.

Default Value

This will depend on the CNI plugin in use.

References

1. https://kubernetes.io/docs/concepts/extend-kubernetes/compute-storage-net/network-plugins/
2. https://docs.cloud.oracle.com/en-us/iaas/Content/ContEng/Concepts/contengoverview.htm

Additional Information

One example here is Flannel (https://github.com/coreos/flannel) which does not support Network policy unless Calico is also in use.

CIS Controls

MITRE ATT&CK Mappings