Cis Ubuntu1404 V210 6 2 16

---
name: "CIS Ubuntu 14.04 LTS - 6.2.16 Ensure no duplicate UIDs exist"
description: "Verify no duplicate User IDs exist in /etc/passwd"
category: "cis-os-hardening"
version: "2.1.0"
author: "cyberstrike-official"
tags:
  - cis
  - ubuntu
  - ubuntu-14.04
  - level-1
  - scored
  - user-accounts
cis_id: "6.2.16"
cis_benchmark: "CIS Ubuntu Linux 14.04 LTS Benchmark v2.1.0"
tech_stack:
  - ubuntu
  - linux
cwe_ids: []
chains_with: []
prerequisites: []
severity_boost: "medium"
---

# 6.2.16 Ensure no duplicate UIDs exist (Scored)

## Profile Applicability

- Level 1 - Server
- Level 1 - Workstation

## Description

Although the `useradd` program will not let you create a duplicate User ID (UID), it is possible for an administrator to manually edit the `/etc/passwd` file and change the UID field.

## Rationale

Users must be assigned unique UIDs for accountability and to ensure appropriate access protections.

## Audit Procedure

Run the following script and verify no results are returned:

```bash
#!/bin/bash

cat /etc/passwd | cut -f3 -d":" | sort -n | uniq -c | while read x ; do
  [ -z "${x}" ] && break
  set - $x
  if [ $1 -gt 1 ]; then
    users=`awk -F: '($3 == n) { print $1 }' n=$2 /etc/passwd | xargs`
    echo "Duplicate UID ($2): ${users}"
  fi
done
```

## Expected Result

No output should be returned.

## Remediation

Based on the results of the audit script, establish unique UIDs and review all files owned by the shared UIDs to determine which UID they are supposed to belong to.

## Default Value

Not applicable.

## References

None

## CIS Controls

16 Account Monitoring and Control - Account Monitoring and Control

## Profile

- Level 1