CVE-2020-36866
📋 TL;DR
This cross-site scripting (XSS) vulnerability in Nagios XI allows attackers to inject malicious scripts into the Manage Users page of the Admin interface. When exploited, these scripts execute in victims' browsers, potentially stealing session cookies or performing unauthorized actions. Organizations running Nagios XI versions before 5.7.3 are affected.
💻 Affected Systems
- Nagios XI
📦 What is this software?
Nagios Xi by Nagios
⚠️ Risk & Real-World Impact
Worst Case
Attacker steals admin session cookies, gains full administrative access to Nagios XI, and potentially compromises the entire monitoring infrastructure or uses it as a pivot point to attack other systems.
Likely Case
Attacker steals user session cookies to gain unauthorized access to Nagios XI, modifies monitoring configurations, or creates backdoor admin accounts.
If Mitigated
Script execution is blocked by browser security features or web application firewalls, resulting in no impact beyond failed injection attempts.
🎯 Exploit Status
Exploitation requires authenticated access to the Admin interface. Attackers would need to trick authenticated users into visiting a maliciously crafted Manage Users page.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 5.7.3 and later
Vendor Advisory: https://www.nagios.com/changelog/nagios-xi/
Restart Required: No
Instructions:
1. Backup your Nagios XI configuration and data. 2. Download Nagios XI 5.7.3 or later from the official Nagios website. 3. Follow the upgrade instructions in the Nagios XI documentation. 4. Verify the upgrade completed successfully.
🔧 Temporary Workarounds
Implement Web Application Firewall (WAF)
allDeploy a WAF with XSS protection rules to block malicious script injection attempts.
Restrict Admin Interface Access
allLimit access to the Nagios XI Admin interface to trusted IP addresses only using network ACLs or firewall rules.
🧯 If You Can't Patch
- Implement strict Content Security Policy (CSP) headers to prevent script execution from untrusted sources.
- Monitor and audit all user management activities in Nagios XI for suspicious changes.
🔍 How to Verify
Check if Vulnerable:
Check the Nagios XI version in the Admin interface under 'Help' > 'About'. If version is below 5.7.3, the system is vulnerable.Check Version:
cat /usr/local/nagiosxi/var/xiversionVerify Fix Applied:
After upgrading, verify the version shows 5.7.3 or higher in the 'About' page. Test the Manage Users page functionality to ensure it works without errors.📡 Detection & Monitoring
Log Indicators:
- Unusual user management activities
- Multiple failed login attempts followed by successful admin login
- Suspicious strings containing script tags in user-related requests
Network Indicators:
- HTTP requests to Nagios XI containing script injection patterns in user management parameters
SIEM Query:
source="nagios_xi_logs" AND (event="user_modified" OR event="user_created") AND (user_agent CONTAINS "script" OR referer CONTAINS "javascript:")