RHEL 9 must implement address space layout randomization (ASLR) to protect its memory from unauthorized code execution.

Severity	Group ID	Group Title	Version	Rule ID	Date	STIG Version
medium	V-257809	SRG-OS-000433-GPOS-00193	RHEL-09-213070	SV-257809r1155709_rule	2025-11-24	2

Description
Some adversaries launch attacks with the intent of executing code in nonexecutable regions of memory or in memory locations that are prohibited. Security safeguards employed to protect memory include, for example, data execution prevention and address space layout randomization. Data execution prevention safeguards can be either hardware-enforced or software-enforced with hardware providing the greater strength of mechanism. Examples of attacks are buffer overflow attacks. The sysctl --system command will load settings from all system configuration files. All configuration files are sorted by their filename in lexicographical order, regardless of the directories in which they reside. If multiple files specify the same option, the entry in the file with the lexicographically latest name will take precedence. Files are read from directories in the following list from top to bottom. Once a file of a given filename is loaded, any file of the same name in subsequent directories is ignored. /etc/sysctl.d/.conf /run/sysctl.d/.conf /usr/local/lib/sysctl.d/.conf /usr/lib/sysctl.d/.conf /lib/sysctl.d/*.conf /etc/sysctl.conf Satisfies: SRG-OS-000433-GPOS-00193, SRG-OS-000480-GPOS-00227

Description

Some adversaries launch attacks with the intent of executing code in nonexecutable regions of memory or in memory locations that are prohibited. Security safeguards employed to protect memory include, for example, data execution prevention and address space layout randomization. Data execution prevention safeguards can be either hardware-enforced or software-enforced with hardware providing the greater strength of mechanism. Examples of attacks are buffer overflow attacks. The sysctl --system command will load settings from all system configuration files. All configuration files are sorted by their filename in lexicographical order, regardless of the directories in which they reside. If multiple files specify the same option, the entry in the file with the lexicographically latest name will take precedence. Files are read from directories in the following list from top to bottom. Once a file of a given filename is loaded, any file of the same name in subsequent directories is ignored. /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf /lib/sysctl.d/*.conf /etc/sysctl.conf Satisfies: SRG-OS-000433-GPOS-00193, SRG-OS-000480-GPOS-00227

ℹ️ Check
Verify RHEL 9 is implementing ASLR. Check the status of the "kernel.randomize_va_space" kernel parameter with the following command: $ sudo sysctl kernel.randomize_va_space kernel.randomize_va_space = 2 If "kernel.randomize_va_space" is not set to "2" or is missing, this is a finding.

✔️ Fix
Configure RHEL 9 to implement ASLR. Create the drop-in if it does not already exist: $ sudo vi /etc/sysctl.d/99-kernel_randomize_va_space.conf Add the following line to the file: kernel.randomize_va_space = 2 Reload settings from all system configuration files with the following command: $ sudo sysctl --system