CVE-2020-28900
📋 TL;DR
This vulnerability allows attackers to escalate privileges to root or execute arbitrary code on Nagios Fusion and Nagios XI systems by exploiting insufficient verification of update package authenticity. Attackers can upload malicious update packages that get executed with root privileges during the update process. Affected systems include Nagios Fusion 4.1.8 and earlier and Nagios XI 5.7.5 and earlier.
💻 Affected Systems
- Nagios Fusion
- Nagios XI
📦 What is this software?
Fusion by Nagios
Nagios Xi by Nagios
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with root-level code execution, allowing attackers to install persistent backdoors, steal sensitive monitoring data, and pivot to other systems.
Likely Case
Privilege escalation to root followed by installation of cryptocurrency miners, data exfiltration, or ransomware deployment.
If Mitigated
Limited impact if proper network segmentation and least privilege principles are implemented, though root compromise remains possible.
🎯 Exploit Status
Exploitation requires some level of access to trigger the update process, but detailed proof-of-concept code is publicly available making attacks straightforward.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Nagios Fusion 4.1.9+, Nagios XI 5.7.6+
Vendor Advisory: https://www.nagios.com/downloads/nagios-xi/change-log/
Restart Required: Yes
Instructions:
1. Backup current configuration and data. 2. Download the latest version from Nagios official site. 3. Follow the upgrade instructions in the Nagios documentation. 4. Verify the update completed successfully. 5. Restart Nagios services.
🔧 Temporary Workarounds
Disable automatic updates
linuxPrevent automatic update checks and downloads that could be exploited
# Edit Nagios configuration to disable auto-update
# Check documentation for specific configuration parameters
Restrict update script permissions
linuxRemove execute permissions from vulnerable update scripts
chmod -x /usr/local/nagiosfusion/upgrade_to_latest.sh
chmod -x /usr/local/nagiosxi/upgrade_to_latest.sh
🧯 If You Can't Patch
- Implement strict network segmentation to isolate Nagios systems from production networks
- Deploy application control to prevent execution of unauthorized scripts and monitor for suspicious update activities
🔍 How to Verify
Check if Vulnerable:
Check Nagios version: For Nagios XI: cat /usr/local/nagiosxi/var/xiversion | head -1. For Nagios Fusion: cat /usr/local/nagiosfusion/var/fusionversion | head -1. If version ≤ 5.7.5 (XI) or ≤ 4.1.8 (Fusion), system is vulnerable.Check Version:
For Nagios XI: cat /usr/local/nagiosxi/var/xiversion | head -1. For Nagios Fusion: cat /usr/local/nagiosfusion/var/fusionversion | head -1Verify Fix Applied:
After patching, verify version shows 5.7.6+ for Nagios XI or 4.1.9+ for Nagios Fusion using the same commands. Also verify the update script has proper signature verification.📡 Detection & Monitoring
Log Indicators:
- Unauthorized access to update scripts
- Suspicious file uploads to update directories
- Unexpected root privilege escalation
- Execution of upgrade_to_latest.sh from unusual sources
Network Indicators:
- Unusual outbound connections from Nagios systems post-update
- Traffic to known malicious update repositories
SIEM Query:
source="nagios.log" AND ("upgrade_to_latest.sh" OR "update package" OR "privilege escalation")🔗 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/
