CVE-2025-55296 is a medium-severity (CVSS 5.5) Cross-site Scripting (XSS) vulnerability in librenms/librenms. EPSS puts its 30-day exploitation probability at 17.0% (97th percentile). A fix is available for librenms/librenms — see the affected versions and patch details below.
LibreNMS allows stored XSS in Alert Template name field
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 CVE-2025-55296.
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
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 | 25.8.0composer require librenms/librenms:^25.8.0 |
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 25.8.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-55296 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 CVE-2025-55296 in your dependencies?
Find it across Packagist, including transitive dependencies.