CVE-2020-28907
📋 TL;DR
CVE-2020-28907 is a critical SSL certificate validation vulnerability in Nagios Fusion that allows attackers to escalate privileges to root or execute arbitrary code. The flaw exists in the update mechanism where untrusted packages can be downloaded without proper certificate validation. 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
Complete system compromise with root-level code execution, allowing attackers to take full control of the Nagios Fusion server and potentially pivot to other systems.
Likely Case
Privilege escalation to root leading to installation of backdoors, data theft, and lateral movement within the network.
If Mitigated
Limited impact if proper network segmentation and least privilege principles are implemented, though the vulnerability still exists.
🎯 Exploit Status
Exploitation requires some level of access to trigger the update mechanism, but the vulnerability is well-documented with public proof-of-concept details available.
🛠️ 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 Nagios Fusion 4.1.9 or later from the official Nagios website. 3. Follow the official upgrade documentation to apply the update. 4. Restart Nagios Fusion services. 5. Verify the update was successful.
🔧 Temporary Workarounds
Disable automatic updates
linuxPrevent the vulnerable update script from being triggered by disabling automatic updates
chmod -x /usr/local/nagiosfusion/scripts/upgrade_to_latest.sh
Network restriction
linuxBlock outbound connections from Nagios Fusion to untrusted update servers
iptables -A OUTPUT -p tcp --dport 443 -d update.nagios.com -j DROP
🧯 If You Can't Patch
- Implement strict network segmentation to isolate Nagios Fusion from critical systems
- Apply strict file permissions and monitor for unauthorized changes to the upgrade_to_latest.sh script
🔍 How to Verify
Check if Vulnerable:
Check Nagios Fusion version: cat /usr/local/nagiosfusion/var/version.txt | grep 'Fusion'Check Version:
cat /usr/local/nagiosfusion/var/version.txt | grep 'Fusion'Verify Fix Applied:
Verify version is 4.1.9 or higher: cat /usr/local/nagiosfusion/var/version.txt | grep 'Fusion' and ensure it shows 4.1.9+📡 Detection & Monitoring
Log Indicators:
- Unusual update attempts in /var/log/nagiosfusion/update.log
- Execution of upgrade_to_latest.sh from unexpected sources
- SSL certificate validation errors in system logs
Network Indicators:
- Outbound HTTPS connections to non-Nagios update servers
- Unusual file downloads to the Nagios Fusion server
SIEM Query:
source="nagiosfusion.logs" AND ("upgrade_to_latest.sh" OR "SSL certificate" OR "update package")🔗 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/
