# Cis Ubuntu1804 V220 1 4 3

> Ensure authentication required for single user mode

- Skill: `cyberstrikeus/cis-ubuntu1804-v220-1-4-3` (Agent Skill)
- Install (CLI): `npx skillmds@latest add cyberstrikeus/cis-ubuntu1804-v220-1-4-3`
- Raw SKILL.md: https://api.skillmd.com/api/skills/cyberstrikeus/cis-ubuntu1804-v220-1-4-3/raw
- Safety review: PASS (external: skill-scanner PASS, skillspector CAUTION)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: cyberstrikeus (https://skillmd.com/u/cyberstrikeus)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/cyberstrikeus/cis-ubuntu1804-v220-1-4-3

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# 1.4.3 Ensure authentication required for single user mode (Automated)

## Profile Applicability

- Level 1 - Server
- Level 1 - Workstation

## Description

Single user mode is used for recovery when the system detects an issue during boot or by manual selection from the bootloader.

## Rationale

Requiring authentication in single user mode prevents an unauthorized user from rebooting the system into single user to gain root privileges without credentials.

## Audit Procedure

### Command Line

Perform the following to determine if a password is set for the `root` user:

```bash
grep -Eq '^root:\$[0-9]' /etc/shadow || echo "root is locked"
```

## Expected Result

No results should be returned.

## Remediation

### Command Line

Run the following command and follow the prompts to set a password for the `root` user:

```bash
passwd root
```

## References

1. NIST SP 800-53 Rev. 5: IA-5

## CIS Controls

| Controls Version | Control                  | IG 1 | IG 2 | IG 3 |
| ---------------- | ------------------------ | ---- | ---- | ---- |
| v8               | 5.2 Use Unique Passwords | X    | X    | X    |
| v7               | 4.4 Use Unique Passwords |      | X    | X    |

## MITRE ATT&CK Mappings

| Techniques / Sub-techniques | Tactics | Mitigations |
| --------------------------- | ------- | ----------- |
| T1548, T1548.000            | TA0005  | M1022       |