Profile Applicability:
 • Level 1

Description:
 The nodev mount option prevents device files from being interpreted on the mounted filesystem. Applying this option to /var helps prevent the creation and use of device files that could be exploited for privilege escalation or unauthorized access.

Rationale:
 Setting the nodev option on /var reduces the risk of device file abuse, which can lead to system compromise or privilege escalation attacks.

Impact:
 Pros:

  • Prevents device file exploitation on /var.

  • Improves overall system security posture.

Cons:

  • May interfere with legitimate use of device files in /var (rare).

Default Value:
 By default, nodev is typically not set on /var unless explicitly configured.

Pre-requisites:

  • Root or sudo privileges to modify /etc/fstab and remount filesystems.

  • /var must be mounted as a separate partition.

Remediation:

Test Plan:

Using Linux command line:

  1. Check current mount options for /var:

     mount | grep /var

  2. Verify if nodev is included in /etc/fstab for /var:

     grep /var /etc/fstab
    Expected output: Mount options for /var include nodev.



Implementation Plan:

Using Linux command line:

  1. Edit /etc/fstab to add nodev to /var mount options. Example:
    /dev/<partition>  /var  ext4  defaults,nodev,nosuid,noexec  0  0

  2. Remount /var with new options without reboot:

     mount -o remount,nodev /var

  3. Verify mount options:

     mount | grep /var


Backout Plan:

Using Linux command line:

  1. Remove nodev from /var mount options in /etc/fstab.

  2. Remount /var without nodev:

     mount -o remount /var

  3. Verify mount options:

     mount | grep /var

References: