CVE-2021-47697
📋 TL;DR
Nagios XI versions before 5.8.0 contain a cross-site scripting vulnerability in the Views feature URL handling. Attackers can inject malicious scripts that execute in victims' browsers when they visit manipulated URLs. This affects all Nagios XI administrators and users who access the web interface.
💻 Affected Systems
- Nagios XI
📦 What is this software?
Nagios Xi by Nagios
⚠️ Risk & Real-World Impact
Worst Case
Attackers could steal administrator session cookies, perform actions as authenticated users, or redirect users to malicious sites, potentially leading to full system compromise if combined with other vulnerabilities.
Likely Case
Attackers steal session cookies or credentials from authenticated users, gaining unauthorized access to the Nagios XI monitoring system.
If Mitigated
With proper input validation and output encoding, the attack fails silently without any impact on users or system functionality.
🎯 Exploit Status
Exploitation requires user interaction (victim must click a malicious link) and some level of social engineering. The attacker needs to craft a specific URL with malicious payload.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 5.8.0
Vendor Advisory: https://www.nagios.com/changelog/nagios-xi/
Restart Required: No
Instructions:
1. Backup your current Nagios XI configuration. 2. Download Nagios XI 5.8.0 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
Input Validation Enhancement
allImplement additional input validation for URL parameters in the Views feature
Not applicable - requires code modification
Output Encoding
allEnsure all user-supplied data in URLs is properly HTML-encoded before rendering
Not applicable - requires code modification
🧯 If You Can't Patch
- Restrict access to Nagios XI web interface to trusted networks only using firewall rules
- Implement a web application firewall (WAF) with XSS protection rules
🔍 How to Verify
Check if Vulnerable:
Check Nagios XI version via the web interface (Help > About) or command line: cat /usr/local/nagiosxi/var/xiversionCheck Version:
cat /usr/local/nagiosxi/var/xiversionVerify Fix Applied:
Verify version is 5.8.0 or higher and test URL parameter handling in Views feature📡 Detection & Monitoring
Log Indicators:
- Unusual URL patterns in web server logs containing script tags or JavaScript in Views-related URLs
- Multiple failed attempts to access Views with malformed parameters
Network Indicators:
- HTTP requests to Nagios XI with suspicious parameters in the URL
- Outbound connections from Nagios XI server to unknown external IPs following Views access
SIEM Query:
source="nagios_access.log" AND (url="*views*" AND (url="*<script>*" OR url="*javascript:*" OR url="*onload=*"))