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UBTU-22-213010 Ubuntu 22.04 LTS must restrict access to the kernel message buffer.

DISA STIG library V2R10
All changes in this version
first version loaded CAT III

Maps to SC-4 via CCI-001090

Title

Ubuntu 22.04 LTS must restrict access to the kernel message buffer.

Control

Verify Ubuntu 22.04 LTS 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 that 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.

Discussion

Restricting access to the kernel message buffer limits access only to root. This prevents attackers from gaining additional system information as a nonprivileged user.

Related controls

CCI-001090

Fix

Configure Ubuntu 22.04 LTS 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