Profile Applicability:
 • Level 1

Description:
 The nodev mount option prevents device files from being interpreted on the mounted filesystem. Applying this option to /tmp protects the system by disallowing device files from being created or used in /tmp.

Rationale:
 Setting the nodev option on /tmp reduces the risk of device file abuse by attackers, which could lead to privilege escalation or unauthorized access.

Impact:
 Pros:

  • Prevents creation and use of device files on /tmp.

  • Helps mitigate privilege escalation attacks.

Cons:

  • May interfere with applications that require device files in /tmp (rare).

Default Value:
 By default, the nodev option is usually not set on /tmp unless configured explicitly.

Pre-requisites:

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

  • /tmp must be mounted as a separate partition.

Remediation:

Test Plan:

Using Linux command line:

  1. Check current mount options on /tmp:

     mount | grep /tmp

  2. Verify if nodev option is present in /etc/fstab for /tmp:

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



Implementation Plan:

Using Linux command line:

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


  2. Remount /tmp to apply the new option without reboot:

     mount -o remount,nodev /tmp

  3. Verify mount options again:

    mount | grep /tmp

Backout Plan:

Using Linux command line:

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

  2. Remount /tmp without nodev:

     mount -o remount /tmp


  3. Verify mount options:

     mount | grep /tmp

References: