GHSA-vxq6-8cwm-wj99
MEDIUMLibreNMS allows stored XSS in Alert Template name field
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Blast Radius
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Description
Summary
A stored Cross-Site Scripting (XSS) vulnerability exists in LibreNMS (<= 25.6.0) in the Alert Template creation feature. This allows a user with the admin role to inject malicious JavaScript, which will be executed when the template is rendered, potentially compromising other admin accounts.
Details
In the LibreNMS web UI, when a user with the admin role visits /templates and clicks "Create new alert template", the "Template name" field fails to properly sanitize input. By inserting a payload like:
<script>alert(document.cookie)</script>
and filling the other fields with arbitrary content (e.g., test), once the template is saved, the script is executed. This confirms that user input is stored and later rendered without proper output encoding.
This vulnerability can be exploited for session hijacking, data theft, or other malicious actions targeting other admin users.
PoC
-
Log in to LibreNMS using an account with the admin role.
-
Navigate to:
http://localhost:8000/templates. -
Click the "Create new alert template" button.
-
Input the following into the Template name field:
<script>alert(document.cookie)</script> -
Fill the remaining fields (
Template,Alert title,Recovery title) with arbitrary content such astest. -
Click "Create template".
-
Upon saving, a JavaScript alert pops up, confirming the stored XSS is triggered.
<img width="1574" height="848" alt="image" src="https://github.com/user-attachments/assets/bc482874-c47e-48e3-83b6-cb4a9dcf4a53" />
Impact
Type: Stored Cross-Site Scripting (XSS)
Affected users: Only accounts with the admin role who access the Alert Templates page (http://localhost:8000/templates) are affected.
Attackers need: Authenticated admin-level access.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | librenms/librenms | all versions | 25.8.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for librenms/librenms. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update librenms/librenms to 25.8.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-vxq6-8cwm-wj99 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-vxq6-8cwm-wj99 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-vxq6-8cwm-wj99. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-vxq6-8cwm-wj99 in your dependencies?
O3 detects GHSA-vxq6-8cwm-wj99 across Packagist dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.