Cis K8s V1111 4.2.4

---
name: cis-k8s-v1111-4.2.4
description: "Verify that if defined, readOnlyPort is set to 0 (Manual)"
category: cis-k8s
version: "1.11.1"
author: cyberstrike-official
tags:
  [
    cis,
    kubernetes,
    worker-nodes,
    kubelet,
    authentication,
    authorization,
    tls,
    streaming,
    iptables,
    hostname-override,
    event-capture,
    certificate-rotation,
    seccomp,
    strong-ciphers,
  ]
cis_id: "4.2.4"
cis_benchmark: "CIS Kubernetes Benchmark v1.11.1"
tech_stack: [kubernetes]
cwe_ids: []
chains_with: []
prerequisites: []
severity_boost: {}
---

# 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    |