How to remediate – Unpassworded ‘root’ Account

1. Introduction

The vulnerability ‘Unpassworded root Account’ means a system administrator account, named ‘root’, has no password set. This allows anyone with local access to gain full control of the system without authentication. Systems commonly affected are Linux and Unix based servers, virtual machines and embedded devices. A successful exploit could lead to complete compromise of confidentiality, integrity, and availability.

2. Technical Explanation

The root account has no password set, allowing immediate access with no credentials required. An attacker needs only local console or SSH access to the system to gain control. This is often due to misconfiguration during initial setup or a deliberate removal of the password for testing purposes. CVE-1999-0502 and CVE-2019-5021 describe similar issues.

• Root cause: The root account lacks a password, bypassing standard authentication mechanisms.
• Exploit mechanism: An attacker simply logs in as ‘root’ without providing a password. For example, on many systems, an attacker could directly log into the console or via SSH and gain immediate access.
• Scope: Primarily affects Linux and Unix-based operating systems including distributions like Debian, Ubuntu, CentOS, Red Hat Enterprise Linux, and macOS.

3. Detection and Assessment

Confirming a vulnerable system requires checking the root account’s password status. A quick check can be performed using standard user management tools. More thorough assessment involves reviewing shadow file contents.

• Quick checks: Use the command `sudo -l` to see if a password is required for root privileges. If no password prompt appears, it’s likely vulnerable.
• Scanning: Nessus vulnerability ID 21986 can detect this issue as an example.
• Logs and evidence: Check system logs (/var/log/auth.log or /var/log/secure) for successful logins by root without a password, though these may not always be logged.

sudo -l

4. Solution / Remediation Steps

Fixing this issue involves setting a strong password for the root account. Follow these steps carefully to avoid locking yourself out of the system.

4.1 Preparation

• No specific dependencies exist, but ensure you know the root account’s password reset procedure for your operating system distribution. A roll back plan involves restoring from backup if issues occur.
• A change window may be needed depending on service criticality and approval policies.

4.2 Implementation

1. Step 1: Use the `passwd` command to set a password for the root account.
2. Step 2: Enter the new password twice when prompted. Choose a strong, unique password.

4.3 Config or Code Example

Before

root:!!:0:0::/:/bin/bash

After

root:$6$rounds=5000$salt$hashed_password:0:0::/:/bin/bash

4.4 Security Practices Relevant to This Vulnerability

Several security practices directly address this vulnerability type.

• Practice 1: Least privilege – Limit the number of accounts with root access and use sudo for specific tasks instead.
• Practice 2: Strong password policies – Enforce strong, unique passwords for all accounts, including root.

4.5 Automation (Optional)

#!/bin/bash
# This script sets a password for the root account on Linux systems.
# Use with caution! Ensure you have appropriate backups.
passwd root << EOF
new_password
new_password
EOF

5. Verification / Validation

Confirming the fix involves verifying that a password is now required to log in as root. Re-run earlier detection methods and perform basic service tests.

• Post-fix check: Run `sudo -l`. A password prompt should appear when attempting to execute commands with root privileges.
• Re-test: Repeat the initial quick check (using `sudo -l`) to confirm a password is now required.
• Monitoring: Monitor system logs (/var/log/auth.log or /var/log/secure) for failed login attempts as root, which could indicate brute-force attacks.

sudo -l

6. Preventive Measures and Monitoring

Several measures can prevent this vulnerability type.

• Baselines: Update security baselines to include a requirement for strong passwords on all accounts, including root.
• Pipelines: Implement configuration management tools that enforce password policies and automatically detect unpassworded accounts.
• Asset and patch process: Regularly review system configurations to ensure compliance with security standards. A monthly config audit is sensible.

7. Risks, Side Effects, and Roll Back

Setting a strong password for root should not cause service impacts, but incorrect configuration could lock you out of the system.

• Risk or side effect 1: Incorrectly configured SSH access could prevent remote login if the password is forgotten. Ensure alternative access methods are available.
• Roll back: Restore from backup if issues occur. If possible, boot into single-user mode to reset the root password manually.

8. References and Resources

• Vendor advisory or bulletin: Red Hat Security Advisories
• NVD or CVE entry: CVE-1999-0502
• Product or platform documentation relevant to the fix: Debian passwd manual page