STIGQter: STIG Summary: Red Hat Enterprise Linux 9 Security Technical Implementation Guide Version: 2 Release: 9 Benchmark Date: 01 Jul 2026:

RHEL 9 must disable the use of user namespaces.

DISA Rule

SV-257816r1155715_rule

Vulnerability Number

V-257816

Group Title

SRG-OS-000480-GPOS-00227

Rule Version

RHEL-09-213105

Severity

CAT II

CCI(s)

• CCI-000366 - Implement the security configuration settings.

Weight

10

Fix Recommendation

Configure RHEL 9 to disable the use of user namespaces.

Create the drop-in if it does not already exist:

$ sudo vi /etc/sysctl.d/99-user_max_user_namespaces.conf

Add the following line to the file:

user.max_user_namespaces = 0

Reload settings from all system configuration files with the following command:

$ sudo sysctl --system

Check Contents

Verify RHEL 9 disables the use of user namespaces.

Check the status of the "user.max_user_namespaces" parameter with the following command:

$ sudo sysctl user.max_user_namespaces

user.max_user_namespaces = 0

If "user.max_user_namespaces" is not set to "0" or is missing, this is a finding.

If the use of namespaces is operationally required and documented with the information system security manager (ISSM), it is not a finding.

Vulnerability Number

V-257816

Documentable

False

Rule Version

RHEL-09-213105

Severity Override Guidance

Verify RHEL 9 disables the use of user namespaces.

Check the status of the "user.max_user_namespaces" parameter with the following command:

$ sudo sysctl user.max_user_namespaces

user.max_user_namespaces = 0

If "user.max_user_namespaces" is not set to "0" or is missing, this is a finding.

If the use of namespaces is operationally required and documented with the information system security manager (ISSM), it is not a finding.

Check Content Reference

M

Target Key

5551