Ubuntu 24.04 LTS must restrict access to the kernel message buffer.

Severity	Group ID	Group Title	Version	Rule ID	Date	STIG Version
low	V-270749	SRG-OS-000138-GPOS-00069	UBTU-24-600140	SV-270749r1067179_rule	2025-02-18	1

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.

ℹ️ Check
Verify Ubuntu 24.04 LTS is configured to restrict access to the kernel message buffer with 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 -r 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 any instance of "kernel.dmesg_restrict" is uncommented and set to "0", or if conflicting results are returned, this is a finding.

ℹ️ Check

Verify Ubuntu 24.04 LTS is configured to restrict access to the kernel message buffer with 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 -r 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 any instance of "kernel.dmesg_restrict" is uncommented and set to "0", or if conflicting results are returned, this is a finding.

✔️ Fix
Configure Ubuntu 24.04 LTS to restrict access to the kernel message buffer. Set the system to the required kernel parameter by adding or modifying the following line in /etc/sysctl.conf or a config file in the /etc/sysctl.d/ directory: 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 with the following command: $ sudo sysctl --system

✔️ Fix

Configure Ubuntu 24.04 LTS to restrict access to the kernel message buffer. Set the system to the required kernel parameter by adding or modifying the following line in /etc/sysctl.conf or a config file in the /etc/sysctl.d/ directory: 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 with the following command: $ sudo sysctl --system