cis-k8s-v200-4-3-1

name	cis-k8s-v200-4.3.1
description	Ensure that the kube-proxy metrics service is bound to localhost (Manual)
category	cis-k8s
version	2.0.0
author	cyberstrike-official
tags	["cis","kubernetes","worker-node","kube-proxy","metrics","network-binding"]
cis_id	4.3.1
cis_benchmark	CIS Kubernetes Benchmark v2.0.0
tech_stack	["kubernetes"]
cwe_ids	[]
chains_with	[]
prerequisites	[]
severity_boost	{}

4.3.1 Ensure that the kube-proxy metrics service is bound to localhost (Manual)

Profile Applicability

• Level 1 - Worker Node

Description

Do not bind the kube-proxy metrics port to non-loopback addresses.

Rationale

kube-proxy has two APIs which provided access to information about the service and can be bound to network ports. The metrics API service includes endpoints (/metrics and /configz) which disclose information about the configuration and operation of kube-proxy. These endpoints should not be exposed to untrusted networks as they do not support encryption or authentication to restrict access to the data they provide.

Impact

3rd party services which try to access metrics or configuration information related to kube-proxy will require access to the localhost interface of the node.

Audit

review the start-up flags provided to kube proxy

Run the following command on each node:

ps -ef | grep -i kube-proxy

Ensure that the --metrics-bind-address parameter is not set to a value other than 127.0.0.1. From the output of this command gather the location specified in the --config parameter. Review any file stored at that location and ensure that it does not specify a value other than 127.0.0.1 for metricsBindAddress.

Remediation

Modify or remove any values which bind the metrics service to a non-localhost address.

Default Value

The default value is 127.0.0.1:10249.

References

1. https://kubernetes.io/docs/reference/command-line-tools-reference/kube-proxy/

CIS Controls

Controls Version	Control	IG 1	IG 2	IG 3
v8	12.6 Use of Secure Network Management and Communication Protocols - Use secure network management and communication protocols (e.g., 802.1X, Wi-Fi Protected Access 2 (WPA2) Enterprise or greater).		*	*
v7	9.2 Ensure Only Approved Ports, Protocols and Services Are Running - Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system.		*	*