LibreNMS alert-rules has a Cross-Site Scripting VulnerabilityGHSA-6g2v-66ch-6xmh
LOWFix: librenms/librenms@dccdf67GHSA-6g2v-66ch-6xmh is a low-severity (CVSS 3.8) Cross-site Scripting (XSS) vulnerability in librenms/librenms. A fix is available for librenms/librenms — see the affected versions and patch details below.
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
Exploitation and automatability from CISA’s SSVC triage for GHSA-6g2v-66ch-6xmh.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
librenms/librenmsReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.
Description
Executive Summary
Product: LibreNMS
Vendor: LibreNMS
Vulnerability Type: Cross-Site Scripting (XSS)
CVSS Score: 4.3 (AV:N/AC:L/PR:H/UI:R/S:U/C:L/I:L/A:L)
Affected Version: 25.8.0 (latest at time of discovery)
POC File: Download POC
Ticket: ZDI-CAN-28105: LibreNMS Alert Rules Cross-Site Scripting Vulnerability
Vulnerability Details
Description
Trend Micro's Zero Day Initiative has identified a Cross-Site Scripting vulnerability in LibreNMS. The vulnerability exists in the Alert Rules functionality where the alert rule name is not properly sanitized, allowing injection of HTML code.
Technical Details
Version Tested: 25.8.0
Installer File: 25.8.0.tar.gz
Download Link: https://github.com/librenms/librenms/archive/refs/tags/25.8.0.tar.gz
Platform: N/A
Attack Vector
When browsing to Alerts > Alert Rules page, a LibreNMS admin can add and manage alert rules. The alert rule name field is vulnerable to XSS attacks through improper sanitization.
Root Cause Analysis
Vulnerable Request
When creating or updating an alert rule, the following HTTP POST request is sent to /ajax_form.php:
POST /ajax_form.php HTTP/1.1
...
_token=9YjTntCuMIe2ujpumwqJQoENRXUhJzlDt33Xu7kx&device_id=-1&device_name=&rule_id=&type=alert-rules&template_id=&builder_json=%7B%22condition%22%3A%22AND%22%2C%22rules%22%3A%5B%7B%22id%22%3A%22access_points.accesspoint_id%22%2C%22field%22%3A%22access_points.accesspoint_id%22%2C%22type%22%3A%22string%22%2C%22input%22%3A%22text%22%2C%22operator%22%3A%22equal%22%2C%22value%22%3A%2242%22%7D%5D%2C%22valid%22%3Atrue%7D&name=%3Ci%3Efoo%3C%2Fi%3E&builder_rule_0_filter=access_points.accesspoint_id&builder_rule_0_operator=equal&builder_rule_0_value_0=42&severity=warning&count=1&delay=1m&interval=5m&recovery=on&acknowledgement=on&proc=¬es=&adv_query=
Code Flow
- Request Processing: PHP script
includes/html/forms/alert-rules.inc.phpprocesses the request - Sanitization Attempt: Calls
strip_tags()to sanitize thenameparameter - Database Operation: Calls
dbUpdate()ordbInsert()to save the rule
Bypass Technique
The sanitization can be bypassed using XML character references:
<script>alert(1)</script>
Execution Path
- Page Load: Victim browses to Alerts > Alert Rules page
- Script Execution:
includes/html/print-alert/rules.phpis called - Modal Inclusion: Includes
includes/html/modal/alert_rule_list.inc.phpwhich returns HTML for modal window - Table Rendering: Modal contains HTML table with all rules and inline JavaScript calling
bootgrid()function - XSS Trigger: The
bootgrid()function (http://www.jquery-bootgrid.com/) rewrites table cells, decoding XML character references - Code Execution: Browser interprets the decoded payload as HTML tags and executes the injected script
Proof of Concept
Usage
python3 poc.py client ip_addr -U <username> -P <password>
Optional Parameters
-E [kvp|multipart]- Specify HTTP request parameter encoding
Credit
Discovered by: Simon Humbert of Trend Research, Trend Micro
About Zero Day Initiative (ZDI)
Established by TippingPoint and acquired by Trend Micro, the Zero Day Initiative (ZDI) neither re-sells vulnerability details nor exploit code. Instead, upon notifying the affected product vendor, the ZDI provides its Trend Micro TippingPoint customers with zero day protection through its intrusion prevention technology. Explicit details regarding the specifics of the vulnerability are not exposed to any parties until an official vendor patch is publicly available.
References
- ZDI Website: http://www.zerodayinitiative.com
- Disclosure Policy: http://www.zerodayinitiative.com/advisories/disclosure_policy/
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | librenms/librenms | all versions | 25.10.0composer require librenms/librenms:^25.10.0 |
Affected Products
librenmslibrenmsDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for librenms/librenms, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update librenms/librenms to 25.10.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-6g2v-66ch-6xmh is resolved across your whole dependency graph.
Workarounds
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.
Frequently Asked Questions
Is GHSA-6g2v-66ch-6xmh in your dependencies?
Find it across Packagist, including transitive dependencies.