cis-ubuntu1804-v220-4-2-7

name	cis-ubuntu1804-v220-4-2-7
description	Ensure sshd DisableForwarding is enabled
category	cis-networking
version	2.2.0
author	cyberstrike-official
tags	["cis","ubuntu","linux","ubuntu-18.04","ssh","remote-access"]
cis_id	4.2.7
cis_benchmark	CIS Ubuntu Linux 18.04 LTS Benchmark v2.2.0
tech_stack	["ubuntu","linux"]
cwe_ids	[]
chains_with	[]
prerequisites	[]
severity_boost	{}

CIS Ubuntu Linux 18.04 LTS Benchmark v2.2.0 - Control 4.2.7

Profile Applicability

• Level 2 - Server
• Level 2 - Workstation

Description

DisableForwarding disables all forwarding features, including X11, ssh-agent, TCP and StreamLocal. This overrides all other forwarding-related options and can simplify restricted configurations.

Rationale

Leaving port forwarding mechanisms enabled can expose the organization to security risks and back-channels. SSH includes a port-forwarding mechanism that enables tunneling of network protocols and allows for unauthorized communication to bypass firewall restrictions.

Impact

SSH tunnels are widely used in many corporate environments. In some environments the applications themselves may have limited native support for security and may rely on SSH tunnels for encryption and security. Disabling SSH forwarding may impact these systems. Review the need for SSH forwarding before disabling it.

Audit Procedure

Command Line

Run the following command and verify the output:

sshd -T | grep -i disableforwarding

Expected Result

disableforwarding yes

Remediation

Command Line

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

DisableForwarding yes

Default Value

DisableForwarding no

References

1. NIST SP 800-53 Rev. 5: CM-7

CIS Controls

v8 - 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software - Uninstall or disable unnecessary services on enterprise assets and software, such as an unused file sharing service, web application module, or service function.

v7 - 9.2 Ensure Only Approved Ports, Protocols, and Services Are Running.

Profile Applicability

• Level 2 - Server
• Level 2 - Workstation

Assessment Status

Automated