cis-ubuntu-14-04-lts-5-2-4-ensure-ssh-x11-forwarding-is-disabled

name	CIS Ubuntu 14.04 LTS - 5.2.4 Ensure SSH X11 forwarding is disabled
description	Verify SSH X11 forwarding is disabled to prevent remote graphic connection tunneling
category	cis-os-hardening
version	2.1.0
author	cyberstrike-official
tags	["cis","ubuntu","ubuntu-14.04","level-1","scored","ssh"]
cis_id	5.2.4
cis_benchmark	CIS Ubuntu Linux 14.04 LTS Benchmark v2.1.0
tech_stack	["ubuntu","linux"]
cwe_ids	[]
chains_with	[]
prerequisites	[]
severity_boost	medium

5.2.4 Ensure SSH X11 forwarding is disabled (Scored)

Profile Applicability

• Level 1 - Server
• Level 1 - Workstation

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

Run the following command and verify that output matches:

grep "^X11Forwarding" /etc/ssh/sshd_config

Expected Result

X11Forwarding no

Remediation

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

X11Forwarding no

Default Value

X11Forwarding yes

References

• CIS Controls: 3.4 - Use Only Secure Channels For Remote System Administration

Profile

• Level 1 - Server
• Level 1 - Workstation