Ubuntu OS must restrict access to the kernel message buffer.
Overview
| Finding ID | Version | Rule ID | IA Controls | Severity |
| V-275567 | RIIM-OS-213010 | SV-275567r1147751_rule | CCI-001090 | medium |
| Description | ||||
| Restricting access to the kernel message buffer limits access only to root. This prevents attackers from gaining additional system information as a nonprivileged user. | ||||
| STIG | Date | |||
| Riverbed NetIM OS Security Technical Implementation Guide | 2025-10-02 | |||
Details
Check Text (C-275567r1147751_chk)
Verify Ubuntu OS is configured to restrict access to the kernel message buffer by using the following command:
$ sysctl kernel.dmesg_restrict
kernel.dmesg_restrict = 1
If "kernel.dmesg_restrict" is not set to "1" or is missing, this is a finding.
Verify there are no configurations that enable the kernel dmesg function:
$ sudo grep -ir kernel.dmesg_restrict /run/sysctl.d/* /etc/sysctl.d/* /usr/local/lib/sysctl.d/* /usr/lib/sysctl.d/* /lib/sysctl.d/* /etc/sysctl.conf 2> /dev/null
/etc/sysctl.d/10-kernel-hardening.conf:kernel.dmesg_restrict = 1
If "kernel.dmesg_restrict" is not set to "1", is commented out, is missing, or conflicting results are returned, this is a finding.
Fix Text (F-79574r1147750_fix)
Configure Ubuntu OS to restrict access to the kernel message buffer.
Add or modify the following line in the "/etc/sysctl.conf" file:
kernel.dmesg_restrict = 1
Remove any configurations that conflict with the above from the following locations:
/run/sysctl.d/
/etc/sysctl.d/
/usr/local/lib/sysctl.d/
/usr/lib/sysctl.d/
/lib/sysctl.d/
/etc/sysctl.conf
Reload settings from all system configuration files by using the following command:
$ sudo sysctl --system
Note: This is set by default as part of the NetIM Ubuntu baseline.