cis-ubuntu1604-v200-3-3-9

name	cis-ubuntu1604-v200-3-3-9
description	Ensure IPv6 router advertisements are not accepted
category	cis-networking
version	2.0.0
author	cyberstrike-official
tags	["cis","ubuntu","linux","ubuntu-16.04","networking"]
cis_id	3.3.9
cis_benchmark	CIS Ubuntu Linux 16.04 LTS Benchmark v2.0.0
tech_stack	["ubuntu","linux"]
cwe_ids	[]
chains_with	[]
prerequisites	[]
severity_boost	{}

CIS Ubuntu Linux 16.04 LTS Benchmark v2.0.0 - Control 3.3.9

Description

This setting disables the system's ability to accept IPv6 router advertisements.

Rationale

It is recommended that systems do not accept router advertisements as they could be tricked into routing traffic to compromised machines. Setting hard routes within the system (usually a single default route to a trusted router) protects the system from bad routes.

Impact

None.

Audit Procedure

Command Line

IF IPv6 is enabled:

Run the following commands and verify output matches:

sysctl net.ipv6.conf.all.accept_ra

sysctl net.ipv6.conf.default.accept_ra

grep "net\.ipv6\.conf\.all\.accept_ra" /etc/sysctl.conf /etc/sysctl.d/*

grep "net\.ipv6\.conf\.default\.accept_ra" /etc/sysctl.conf /etc/sysctl.d/*

OR verify IPv6 is disabled:

Run the following script. Output will confirm if IPv6 is disabled on the system.

#!/usr/bin/bash
output=""
grubfile="$(find -L /boot -name 'grub.cfg' -type f)"
[ -f "$grubfile" ] && ! grep "^\s*linux" "$grubfile" | grep -vq ipv6.disable=1 && output="ipv6 disabled in grub config"
grep -Eqs "^\s*net\.ipv6\.conf\.all\.disable_ipv6\s*=\s*1\b" /etc/sysctl.conf /etc/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf /run/sysctl.d/*.conf && grep -Eqs "^\s*net\.ipv6\.conf\.default\.disable_ipv6\s*=\s*1\b" /etc/sysctl.conf /etc/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf /run/sysctl.d/*.conf && sysctl net.ipv6.conf.all.disable_ipv6 | grep -Eq "^\s*net\.ipv6\.conf\.all\.disable_ipv6\s*=\s*1\b" && sysctl net.ipv6.conf.default.disable_ipv6 | grep -Eq "^\s*net\.ipv6\.conf\.default\.disable_ipv6\s*=\s*1\b" && output="ipv6 disabled in sysctl config"
[ -n "$output" ] && echo -e  ||  -e