AlmaLinux OS 9 must disable mounting of cramfs.

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.

Verify that AlmaLinux OS 9 disables the ability to load the cramfs kernel module with the following command:

$ grep 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, create a *.conf file in /etc/modprobe.d/ with the following content:

install cramfs /bin/false blacklist cramfs