The Ubuntu operating system default filesystem permissions must be defined in such a way that all authenticated users can read and modify only their own files.
Overview
| Finding ID | Version | Rule ID | IA Controls | Severity |
| V-238209 | UBTU-20-010016 | SV-238209r991590_rule | CCI-000366 | medium |
| Description | ||||
| Setting the most restrictive default permissions ensures that when new accounts are created they do not have unnecessary access. | ||||
| STIG | Date | |||
| Canonical Ubuntu 20.04 LTS Security Technical Implementation Guide | 2025-05-16 | |||
Details
Check Text (C-238209r991590_chk)
Verify the Ubuntu operating system defines default permissions for all authenticated users in such a way that the user can read and modify only their own files.
Verify the Ubuntu operating system defines default permissions for all authenticated users with the following command:
$ grep -i "umask" /etc/login.defs
UMASK 077
If the "UMASK" variable is set to "000", this is a finding with the severity raised to a CAT I.
If the value of "UMASK" is not set to "077", is commented out, or is missing completely, this is a finding.
Fix Text (F-41378r653801_fix)
Configure the system to define the default permissions for all authenticated users in such a way that the user can read and modify only their own files.
Edit the "UMASK" parameter in the "/etc/login.defs" file to match the example below:
UMASK 077