CVE-2024-50351: 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 "reportthis()" 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')();<%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 "reportthis()" 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')();<%2fscript> 2. Access the page with the injected payload. 3. Observe that the injected script executes when the page is loaded.

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

Example Request: http GET /device/device=1/tab=logs/section=%3Cscript%3Econstructor'constructor')();%3C%2fscript%3E/ HTTP/1.1 Host: <yourhost> Cookie: <yourcookie>

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.