Title

TOSS must disable mounting of cramfs. (Cat II impact)

Discussion

It is detrimental for operating systems to provide, or install by default, functionality exceeding requirements or mission objectives. These unnecessary capabilities or services are often overlooked and therefore may remain unsecured. They increase the risk to the platform by providing additional attack vectors. Removing support for unneeded filesystem types reduces the local attack surface of the server. Compressed ROM/RAM file system (or cramfs) is a read-only file system designed for simplicity and space efficiency. It is mainly used in embedded and small footprint systems.

Check Content

Verify the operating system disables the ability to load the cramfs kernel module. $ sudo grep -r cramfs /etc/modprobe.d/* | grep install install cramfs /bin/false If the command does not return any output, or the line is commented out, and use of the cramfs protocol is not documented with the Information System Security Officer (ISSO) as an operational requirement, this is a finding. Verify the operating system disables the ability to use the cramfs kernel module. Check to see if the cramfs kernel module is disabled with the following command: $ sudo grep -r cramfs /etc/modprobe.d/* | grep "blacklist" blacklist cramfs If the command does not return any output or the output is not "blacklist cramfs", and use of the cramfs kernel module is not documented with the Information System Security Officer (ISSO) as an operational requirement, this is a finding.

Fix Text

Configure the operating system to disable the ability to use the cramfs kernel module. Add or update the following lines in the file "/etc/modprobe.d/blacklist.conf": install cramfs /bin/false blacklist cramfs Reboot the system for the settings to take effect.

Additional Identifiers

Rule ID: SV-253072r958478_rule

Vulnerability ID: V-253072

Group Title: SRG-OS-000095-GPOS-00049

Expert Comments

CCIs tied to check.

Controls tied to check. These are derived from the CCIs shown above.