# Cis K8S V1111 4.2.4

> Verify that if defined, readOnlyPort is set to 0 (Manual)

- Skill: `cyberstrikeus/cis-k8s-v1111-4-2-4` (Agent Skill)
- Install (CLI): `npx skillmds@latest add cyberstrikeus/cis-k8s-v1111-4-2-4`
- Raw SKILL.md: https://api.skillmd.com/api/skills/cyberstrikeus/cis-k8s-v1111-4-2-4/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-v1111-4-2-4

---


# 4.2.4 Verify that if defined, readOnlyPort is set to 0 (Manual)

## Profile Applicability

- Level 1 - Worker Node

## Description

Disable the read-only port.

## Rationale

The Kubelet process provides a read-only API in addition to the main Kubelet API. Unauthenticated access is provided to this read-only API which could possibly retrieve potentially sensitive information about the cluster.

## Impact

Removal of the read-only port will require that any service which made use of it will need to be re-configured to use the main Kubelet API.

## Audit

Run the following command on each node:

```bash
ps -ef | grep kubelet
```

Verify that the `--read-only-port` argument exists and is set to `0`.
If the `--read-only-port` argument is not present, check that there is a Kubelet config file specified by `--config`. Check that if there is a `readOnlyPort` entry in the file, it is set to `0`.

## Remediation

If using a Kubelet config file, edit the file to set `readOnlyPort` to `0`.
If using command line arguments, edit the kubelet service file `/etc/kubernetes/kubelet.conf` on each worker node and set the below parameter in `KUBELET_SYSTEM_PODS_ARGS` variable.

```
--read-only-port=0
```

Based on your system, restart the `kubelet` service. For example:

```bash
systemctl daemon-reload
systemctl restart kubelet.service
```

## Default Value

By default, `--read-only-port` is set to `10255/TCP`.

## References

1. [https://kubernetes.io/docs/admin/kubelet/](https://kubernetes.io/docs/admin/kubelet/)
2. [https://github.com/kubernetes/kubernetes/blob/6cedc0853faa118df0ba3d41b48b993422ad3df6/staging/src/k8s.io/kubelet/config/v1beta1/types.go#L142](https://github.com/kubernetes/kubernetes/blob/6cedc0853faa118df0ba3d41b48b993422ad3df6/staging/src/k8s.io/kubelet/config/v1beta1/types.go#L142)

## Additional Information

[https://kubernetes.io/docs/reference/command-line-tools-reference/kubelet/](https://kubernetes.io/docs/reference/command-line-tools-reference/kubelet/)

## CIS Controls

| Controls Version | Control                                                                         | IG 1 | IG 2 | IG 3 |
| ---------------- | ------------------------------------------------------------------------------- | ---- | ---- | ---- |
| v8               | 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software |      | x    | x    |
| v7               | 9.2 Ensure Only Approved Ports, Protocols and Services Are Running              |      | x    | x    |