AlmaLinux OS 9 must disable mounting of squashfs.
Overview
| Finding ID | Version | Rule ID | IA Controls | Severity |
| V-269346 | ALMA-09-030160 | SV-269346r1050228_rule | Medium |
| Description |
| Removing support for unneeded filesystem types reduces the local attack surface of the server. A squashfs compressed filesystem image can be mounted without first decompressing the image. Note that Snap packages use squashfs. |
| STIG | Date |
| CloudLinux AlmaLinux OS 9 Security Technical Implementation Guide | 2025-05-22 |
Details
| Check Text (C-73377r1049528_chk) |
| Verify that AlmaLinux OS 9 disables the ability to load the squashfs kernel module with the following command: $ grep squashfs /etc/modprobe.conf /etc/modprobe.d/* blacklist squashfs If the command does not return any output, or the line is commented out, and use of squashfs is not documented with the information system security officer (ISSO) as an operational requirement, this is a finding. |
| Fix Text (F-73278r1048415_fix) |
| To configure the system to prevent the squashfs kernel module from being loaded, create a *.conf file in /etc/modprobe.d/ with the following content: install squashfs /bin/false blacklist squashfs |