# Cis K8S V1120 5.3.1

> Ensure that the CNI in use supports Network Policies (Manual)

- Skill: `cyberstrikeus/cis-k8s-v1120-5-3-1` (Agent Skill)
- Install (CLI): `npx skillmds@latest add cyberstrikeus/cis-k8s-v1120-5-3-1`
- Raw SKILL.md: https://api.skillmd.com/api/skills/cyberstrikeus/cis-k8s-v1120-5-3-1/raw
- Safety review: PASS (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: DevOps & Infra
- Author: cyberstrikeus (https://skillmd.com/u/cyberstrikeus)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/cyberstrikeus/cis-k8s-v1120-5-3-1

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# 5.3.1 Ensure that the CNI in use supports Network Policies (Manual)

## Profile Applicability

- Level 1 - Master Node

## 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 Procedure

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

## Remediation

If the CNI plugin in use does not support network policies, consideration should be given to making use of a different plugin, or finding an alternate mechanism for restricting traffic in the Kubernetes cluster.

## 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/

## 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

| Controls Version | Control                                        | IG 1 | IG 2 | IG 3 |
| ---------------- | ---------------------------------------------- | ---- | ---- | ---- |
| v8               | 4.4 Implement and Manage a Firewall on Servers | X    | X    | X    |
| v7               | 9.5 Implement Application Firewalls            |      |      | X    |