TOSS 5 must disable mounting of cramfs.

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 file system 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.

Verify TOSS 5 disables the ability to load the "cramfs" kernel module using the following command:

$ sudo grep -r cramfs /etc/modprobe.conf /etc/modprobe.d/* 

blacklist cramfs

If the command does not return any output, or the line is commented out, and use of "cramfs" is not documented with the information system security officer (ISSO) as an operational requirement, this is a finding.

To configure the system to prevent the "cramfs" kernel module from being loaded, add the following line to the file "/etc/modprobe.d/blacklist.conf" (or create blacklist.conf if it does not exist):

install cramfs /bin/false blacklist cramfs