cis-ubuntu1204-v110-9-3-4

name	cis-ubuntu1204-v110-9-3-4
description	Disable SSH X11 Forwarding
category	cis-os-hardening
version	1.1.0
author	cyberstrike-official
tags	["cis","ubuntu",12.04,"linux","authentication","ssh","x11"]
cis_id	9.3.4
cis_benchmark	CIS Ubuntu 12.04 LTS Server Benchmark v1.1.0
tech_stack	["ubuntu","linux"]
cwe_ids	[]
chains_with	[]
prerequisites	[]
severity_boost	{}

9.3.4 Disable SSH X11 Forwarding (Scored)

Profile Applicability

• Level 1

Description

The X11Forwarding parameter provides the ability to tunnel X11 traffic through the connection to enable remote graphic connections.

Rationale

Disable X11 forwarding unless there is an operational requirement to use X11 applications directly. There is a small risk that the remote X11 servers of users who are logged in via SSH with X11 forwarding could be compromised by other users on the X11 server. Note that even if X11 forwarding is disabled, users can always install their own forwarders.

Audit Procedure

Using Command Line

To verify the correct SSH setting, run the following command and verify that the output is as shown:

grep "^X11Forwarding" /etc/ssh/sshd_config

Expected Result

X11Forwarding no

Remediation

Using Command Line

Edit the /etc/ssh/sshd_config file to set the parameter as follows:

X11Forwarding no

Default Value

X11Forwarding yes

References

• CIS Ubuntu 12.04 LTS Server Benchmark v1.1.0

Profile

Level 1 - Scored