| name | cis-ubuntu2004-v300-4-4-3-3 |
| description | Ensure ip6tables outbound and established connections are configured |
| category | cis-networking |
| version | 3.0.0 |
| author | cyberstrike-official |
| tags | ["cis","ubuntu","linux","ubuntu-20.04","firewall","iptables"] |
| cis_id | 4.4.3.3 |
| cis_benchmark | CIS Ubuntu Linux 20.04 LTS Benchmark v3.0.0 |
| tech_stack | ["ubuntu","linux"] |
| cwe_ids | [] |
| chains_with | [] |
| prerequisites | [] |
| severity_boost | {} |
CIS Ubuntu Linux 20.04 LTS Benchmark v3.0.0 - Control 4.4.3.3
Profile
- Level: Level 1 - Server, Level 1 - Workstation
- Assessment Status: Manual
Description
Configure the firewall rules for new outbound, and established IPv6 connections.
Note:
- Changing firewall settings while connected over network can result in being locked out of the system
- Remediation will only affect the active system firewall, be sure to configure the default policy in your firewall management to apply on boot as well
Rationale
If rules are not in place for new outbound, and established connections all packets will be dropped by the default policy preventing network usage.
Audit Procedure
Command Line
Run the following command and verify all rules for new outbound, and established connections match site policy:
ip6tables -L -v -n
- OR -
Verify IPv6 is disabled:
Run the following script. Output will confirm if IPv6 is enabled on the system.
#!/usr/bin/env bash
{
l_ipv6_enabled="is"
! grep -Pqs -- '^\h*0\b' /sys/module/ipv6/parameters/disable && l_ipv6_enabled="is not"
if sysctl net.ipv6.conf.all.disable_ipv6 | grep -Pqs -- "^\h*net\.ipv6\.conf\.all\.disable_ipv6\h*=\h*1\b" \
&& \
sysctl net.ipv6.conf.default.disable_ipv6 | grep -Pqs -- "^\h*net\.ipv6\.conf\.default\.disable_ipv6\h*=\h*1\b"; then
l_ipv6_enabled="is not"
fi
echo -e " - IPv6 $l_ipv6_enabled enabled on the system"
}
Expected Result
Output should show rules matching site policy for outbound and established IPv6 connections. Or IPv6 is disabled.
Remediation
Command Line
Configure iptables in accordance with site policy. The following commands will implement a policy to allow all outbound connections and all established connections:
ip6tables -A OUTPUT -p tcp -m state --state NEW,ESTABLISHED -j ACCEPT
ip6tables -A OUTPUT -p udp -m state --state NEW,ESTABLISHED -j ACCEPT
ip6tables -A INPUT -p tcp -m state --state ESTABLISHED -j ACCEPT
ip6tables -A INPUT -p udp -m state --state ESTABLISHED -j ACCEPT
