AlmaLinux OS 9 must implement nonexecutable data to protect its memory from unauthorized code execution.

ExecShield uses the segmentation feature on all x86 systems to prevent execution in memory higher than a certain address. It writes an address as a limit in the code segment descriptor, to control where code can be executed, on a per-process basis.

When the kernel places the memory regions of a process, such as the stack and heap, higher than this address, the hardware prevents execution in that address range.

Verify ExecShield is enabled on 64-bit AlmaLinux OS 9 systems with the following command:

$ dmesg | grep '[NX|DX]*protection' 

[ 0.000000] NX (Execute Disable) protection: active

If "dmesg" does not show "NX (Execute Disable) protection active", this is a finding.

Update the GRUB 2 bootloader configuration to ensure the noexec kernel parameter is not enabled using the following command:

$ grubby --update-kernel=ALL --remove-args=noexec

Enable the NX bit execute protection in the system BIOS.