RHEL 9 must disable the use of user namespaces.
Overview
| Finding ID | Version | Rule ID | IA Controls | Severity |
| V-257816 | RHEL-09-213105 | SV-257816r1014825_rule | Medium |
| Description |
| User namespaces are used primarily for Linux containers. The value "0" disallows the use of user namespaces. |
| STIG | Date |
| Red Hat Enterprise Linux 9 Security Technical Implementation Guide | 2024-12-04 |
Details
| Check Text (C-61557r1014823_chk) |
| Verify RHEL 9 disables the use of user namespaces with the following commands: $ sudo 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. $ sudo /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. If the use of namespaces is operationally required and documented with the information system security manager (ISSM), this is not a finding. |
| Fix Text (F-61481r1014824_fix) |
| Configure RHEL 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 |