CVE-2020-10819

What it actually does

Cross-site scripting flaw in the LDAP/AD integration component permits injection of arbitrary script via the username parameter that executes in victim browsers with the privileges of the viewing user.

Why it matters to the business

Compromised monitoring consoles can lead to session hijacking, credential theft, and unauthorized changes to critical infrastructure visibility, increasing downtime risk and operational overhead for organizations relying on Nagios XI.

How an attack unfolds

An authenticated high-privileged user submits a crafted username containing HTML/JS payloads to the ldap_ad_integration endpoint; when another administrator later views the component, the payload executes in their session context, enabling theft of cookies or further administrative actions.

How to fix it

Upgrade Nagios XI to a version later than 5.6.11 that contains input sanitization fixes for the LDAP integration component; additionally enforce output encoding on all user-supplied parameters and deploy a web application firewall with XSS filtering rules.

How to confirm the fix worked

Reproduce the vulnerability by submitting test XSS payloads to the username field and confirming that scripts no longer execute; review change logs and perform authenticated scans against the ldap_ad_integration endpoint after patching.

Typical attack path

1. Obtain administrative credentials to Nagios XI
2. Access the includes/components/ldap_ad_integration/ interface
3. Submit username containing script or event-handler payload
4. Induce another privileged user to load the affected view
5. Capture session tokens or perform actions via executed script

How to detect it

Inspect web server access logs for requests to the ldap_ad_integration component that contain suspicious username values with HTML tags, event handlers, or encoded script content; correlate with authenticated user sessions around the time of the request.

• POST /includes/components/ldap_ad_integration/.*username=.*<script
• username parameter containing onerror= or onload=
• requests to ldap_ad_integration containing javascript: or data:text/html

What your security team should do

• Prioritize upgrade of all Nagios XI instances given public exploit availability and high EPSS score
• Enable strict input validation and Content-Security-Policy headers on the web interface
• Audit administrative accounts and review recent access to the LDAP integration pages
• Add SIEM rules to alert on anomalous username values in web request logs