Information
Although the useradd program will not let you create a duplicate User ID (UID), it is possible for an administrator to manually modify passwd(4) and change the UID field.
Users must be assigned unique UIDs for accountability and to ensure appropriate access protections.
Solution
Correct or justify any items discovered in the Audit step. Determine if there exists any users who share a common UID, and work with those users to determine the best course of action in accordance with site policy.