CVE-2020-28904
📋 TL;DR
CVE-2020-28904 is a privilege escalation vulnerability in Nagios Fusion that allows attackers to execute arbitrary PHP code with elevated privileges. Attackers can install malicious components to gain 'nagios' user privileges, potentially leading to full system compromise. This affects Nagios Fusion 4.1.8 and earlier versions.
💻 Affected Systems
- Nagios Fusion
📦 What is this software?
Fusion by Nagios
⚠️ Risk & Real-World Impact
Worst Case
Full system compromise with root-level access, data exfiltration, lateral movement to other systems, and persistent backdoor installation.
Likely Case
Privilege escalation to nagios user, unauthorized access to monitoring data, installation of additional malicious components, and potential pivot to other systems.
If Mitigated
Limited impact with proper network segmentation, minimal privileges, and monitoring in place, potentially only affecting the Nagios Fusion instance.
🎯 Exploit Status
Exploit details and proof-of-concept code are publicly available. Requires some initial access to install malicious components.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Nagios Fusion 4.1.9 and later
Vendor Advisory: https://www.nagios.com/downloads/nagios-xi/change-log/
Restart Required: Yes
Instructions:
1. Backup current configuration and data. 2. Download and install Nagios Fusion 4.1.9 or later from official Nagios website. 3. Follow upgrade instructions in documentation. 4. Restart Nagios Fusion services. 5. Verify functionality.
🔧 Temporary Workarounds
Restrict component installation
linuxLimit who can install components and monitor for unauthorized installation attempts.
chmod 750 /usr/local/nagiosfusion/var/components
chown nagios:nagios /usr/local/nagiosfusion/var/components
Network segmentation
allIsolate Nagios Fusion from critical systems and restrict inbound/outbound connections.
🧯 If You Can't Patch
- Implement strict access controls and monitor for unauthorized component installations
- Deploy network segmentation and limit Nagios Fusion's ability to communicate with other systems
🔍 How to Verify
Check if Vulnerable:
Check Nagios Fusion version: cat /usr/local/nagiosfusion/var/version.installed | grep 'fusion'Check Version:
cat /usr/local/nagiosfusion/var/version.installed | grep 'fusion'Verify Fix Applied:
Verify version is 4.1.9 or later: cat /usr/local/nagiosfusion/var/version.installed | grep 'fusion' and check for '4.1.9' or higher📡 Detection & Monitoring
Log Indicators:
- Unauthorized component installation in Nagios Fusion logs
- Unexpected PHP file execution in system logs
- Privilege escalation attempts in authentication logs
Network Indicators:
- Unusual outbound connections from Nagios Fusion server
- Unexpected file transfers to/from Nagios Fusion
SIEM Query:
source="nagios_fusion.log" AND ("component install" OR "privilege escalation" OR "unauthorized access")🔗 References
- http://packetstormsecurity.com/files/162783/Nagios-XI-Fusion-Privilege-Escalation-Cross-Site-Scripting-Code-Execution.html
- https://skylightcyber.com/2021/05/20/13-nagios-vulnerabilities-7-will-shock-you/
- https://www.nagios.com/downloads/nagios-xi/change-log/
- http://packetstormsecurity.com/files/162783/Nagios-XI-Fusion-Privilege-Escalation-Cross-Site-Scripting-Code-Execution.html
- https://skylightcyber.com/2021/05/20/13-nagios-vulnerabilities-7-will-shock-you/
- https://www.nagios.com/downloads/nagios-xi/change-log/
