CVE-2017-20209
📋 TL;DR
This cross-site scripting vulnerability in Nagios Fusion allows attackers to inject malicious scripts into the Users and Servers pages. When exploited, these scripts execute in victims' browsers, potentially stealing session cookies or performing actions as authenticated users. Organizations running Nagios Fusion versions before 4.0.1 are affected.
💻 Affected Systems
- Nagios Fusion
📦 What is this software?
Fusion by Nagios
⚠️ Risk & Real-World Impact
Worst Case
Attacker steals administrator session cookies, gains full administrative access to Nagios Fusion, and potentially compromises the entire monitoring infrastructure.
Likely Case
Attacker steals user session cookies, gains unauthorized access to monitoring data, and performs limited administrative actions.
If Mitigated
Script execution is blocked by browser security features or web application firewalls, limiting impact to minor UI disruption.
🎯 Exploit Status
Exploitation requires authenticated access to the vulnerable pages. Attack complexity is medium due to the need for social engineering or existing access.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 4.0.1
Vendor Advisory: https://www.nagios.com/changelog/nagios-fusion/
Restart Required: No
Instructions:
1. Backup current Nagios Fusion configuration and data. 2. Download Nagios Fusion 4.0.1 or later from the official Nagios website. 3. Follow the upgrade instructions in the Nagios Fusion documentation. 4. Verify the upgrade completed successfully.
🔧 Temporary Workarounds
Implement Web Application Firewall
allDeploy a WAF with XSS protection rules to block malicious script injection attempts.
Restrict Access to Admin Interface
allLimit access to Nagios Fusion admin interface to trusted IP addresses only.
🧯 If You Can't Patch
- Implement Content Security Policy headers to restrict script execution
- Enable browser security features like XSS filters and disable JavaScript for untrusted users
🔍 How to Verify
Check if Vulnerable:
Check Nagios Fusion version via web interface or command line. Versions below 4.0.1 are vulnerable.Check Version:
grep 'fusion_version' /usr/local/nagiosfusion/html/includes/config.inc.phpVerify Fix Applied:
After upgrading, verify version is 4.0.1 or higher and test XSS payloads no longer execute.📡 Detection & Monitoring
Log Indicators:
- Unusual POST requests to Users or Servers pages with script tags
- Multiple failed login attempts followed by successful access
Network Indicators:
- HTTP requests containing script injection patterns to admin pages
- Outbound connections to suspicious domains from Nagios server
SIEM Query:
source="nagios_access.log" AND (uri_path="/nagiosfusion/admin/users.php" OR uri_path="/nagiosfusion/admin/servers.php") AND (http_method="POST" OR http_method="GET") AND (message="*<script>*" OR message="*javascript:*")