CVE-2019-13451
📋 TL;DR
CVE-2019-13451 is a buffer overflow vulnerability in Xymon's history.c component that allows remote attackers to execute arbitrary code or cause denial of service. This affects Xymon monitoring systems through version 4.3.28. Organizations using vulnerable Xymon installations for network monitoring are at risk.
💻 Affected Systems
- Xymon
📦 What is this software?
Xymon by Xymon
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete system compromise, data theft, and lateral movement within the network.
Likely Case
Denial of service affecting Xymon monitoring capabilities, potentially disrupting network visibility and alerting.
If Mitigated
Limited impact if proper network segmentation and access controls prevent exploitation attempts.
🎯 Exploit Status
Buffer overflow vulnerabilities in widely used monitoring tools are frequently weaponized. Public references and CVSS 9.8 score indicate high exploitability.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 4.3.29 and later
Vendor Advisory: https://lists.xymon.com/archive/2019-July/046570.html
Restart Required: Yes
Instructions:
1. Backup current Xymon configuration. 2. Download Xymon 4.3.29 or later from official sources. 3. Stop Xymon services. 4. Install updated version following vendor instructions. 5. Restart Xymon services. 6. Verify functionality.
🔧 Temporary Workarounds
Network Access Restriction
linuxRestrict network access to Xymon web interface using firewall rules
iptables -A INPUT -p tcp --dport 80 -s trusted_network -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
Web Server Proxy
linuxPlace Xymon behind a reverse proxy with request validation
# Configure nginx/apache as reverse proxy with request size limits
🧯 If You Can't Patch
- Implement strict network segmentation to isolate Xymon systems from critical infrastructure
- Deploy intrusion detection systems to monitor for exploitation attempts and buffer overflow patterns
🔍 How to Verify
Check if Vulnerable:
Check Xymon version: grep 'XYMONVERSION' /usr/lib/xymon/server/etc/version.cfg or similar locationCheck Version:
grep 'XYMONVERSION' /usr/lib/xymon/server/etc/version.cfg 2>/dev/null || xymon --version 2>/dev/null || echo 'Check Xymon documentation for version location'Verify Fix Applied:
Verify version is 4.3.29 or later and check that history.c has been updated with proper bounds checking📡 Detection & Monitoring
Log Indicators:
- Unusual process creation from Xymon web component
- Segmentation fault errors in Xymon logs
- Large or malformed HTTP requests to history.cgi
Network Indicators:
- Unusual traffic patterns to Xymon web port
- Buffer overflow patterns in network traffic
SIEM Query:
source="xymon.log" AND ("segmentation fault" OR "buffer overflow" OR "history.cgi" AND abnormal_request)🔗 References
- https://github.com/svn2github/xymon/blob/master/branches/4.3.28/web/history.c
- https://lists.debian.org/debian-lts-announce/2019/08/msg00032.html
- https://lists.xymon.com/archive/2019-July/046570.html
- https://github.com/svn2github/xymon/blob/master/branches/4.3.28/web/history.c
- https://lists.debian.org/debian-lts-announce/2019/08/msg00032.html
- https://lists.xymon.com/archive/2019-July/046570.html
