AlmaLinux OS 9 must disable the use of user namespaces.
Overview
| Finding ID | Version | Rule ID | IA Controls | Severity |
| V-269284 | ALMA-09-023010 | SV-269284r1101813_rule | CCI-000366 | medium |
| Description | ||||
| User namespaces are used primarily for Linux containers. The value "0" disallows the use of user namespaces. | ||||
| STIG | Date | |||
| CloudLinux AlmaLinux OS 9 Security Technical Implementation Guide | 2025-05-22 | |||
Details
Check Text (C-269284r1101813_chk)
Note: User namespaces are used primarily for Linux containers. If containers are in use, this requirement is Not Applicable.
Verify AlmaLinux OS 9 disables the use of user namespaces with the following commands:
$ sysctl user.max_user_namespaces
user.max_user_namespaces = 0
If the returned line does not have a value of "0", or a line is not returned, this is a finding.
Check that the configuration files are present to enable this kernel parameter.
$ /usr/lib/systemd/systemd-sysctl --cat-config | egrep -v '^(#|;)' | grep -F user.max_user_namespaces | tail -1
user.max_user_namespaces = 0
If the network parameter "user.max_user_namespaces" is not equal to "0", or nothing is returned, this is a finding.
Fix Text (F-73216r1101812_fix)
Configure AlmaLinux OS 9 to disable the use of user namespaces by adding the following line to a file, in the "/etc/sysctl.d" directory:
user.max_user_namespaces = 0
The system configuration files need to be reloaded for the changes to take effect. To reload the contents of the files, run the following command:
$ sudo sysctl --system