cis-ubuntu1604-v200-1-1-1-1

name	cis-ubuntu1604-v200-1-1-1-1
description	Ensure mounting of cramfs filesystems is disabled
category	cis-storage
version	2.0.0
author	cyberstrike-official
tags	["cis","ubuntu","linux","ubuntu-16.04","filesystem","cramfs","kernel-module"]
cis_id	1.1.1.1
cis_benchmark	CIS Ubuntu Linux 16.04 LTS Benchmark v2.0.0
tech_stack	["ubuntu","linux"]
cwe_ids	[]
chains_with	[]
prerequisites	[]
severity_boost	{}

Ensure mounting of cramfs filesystems is disabled

Description

The cramfs filesystem type is a compressed read-only Linux filesystem embedded in small footprint systems. A cramfs image can be used without having to first decompress the image.

Rationale

Removing support for unneeded filesystem types reduces the local attack surface of the server. If this filesystem type is not needed, disable it.

Impact

None noted.

Audit Procedure

Command Line

# modprobe -n -v cramfs | grep -E '(cramfs|install)'
# lsmod | grep cramfs

Expected Result

install /bin/true

The lsmod command should return no output.

Remediation

Command Line

# Edit or create a file in the /etc/modprobe.d/ directory ending in .conf
# Example: vim /etc/modprobe.d/cramfs.conf
# and add the following line:
install cramfs /bin/true

# Run the following command to unload the cramfs module:
rmmod cramfs

Default Value

Not disabled by default.

References

• CIS Controls Version 7 - 5.1 Establish Secure Configurations: Maintain documented, standard security configuration standards for all authorized operating systems and software.

Profile

Level 1 - Server / Level 1 - Workstation, Assessment: Automated