CVE-2020-28653
📋 TL;DR
This vulnerability allows remote attackers to execute arbitrary code on Zoho ManageEngine OpManager systems via the Smart Update Manager (SUM) servlet. It affects OpManager Stable builds before 125203 and Released builds before 125233. Attackers can exploit this without authentication to gain full control of affected systems.
💻 Affected Systems
- Zoho ManageEngine OpManager
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise allowing attackers to install malware, steal sensitive data, pivot to other systems, and maintain persistent access.
Likely Case
Remote code execution leading to ransomware deployment, data exfiltration, or use as a foothold for lateral movement within the network.
If Mitigated
Limited impact if systems are isolated, patched, or have network controls preventing external access to the vulnerable component.
🎯 Exploit Status
Public exploit code exists demonstrating Java deserialization attack via the /servlet/com.adventnet.me.opmanager.servlet.SumPDU endpoint.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Stable build 125203 or later, Released build 125233 or later
Vendor Advisory: https://www.manageengine.com/network-monitoring/help/read-me-complete.html
Restart Required: Yes
Instructions:
1. Download the latest version from ManageEngine website. 2. Backup current installation. 3. Stop OpManager service. 4. Install the update. 5. Restart OpManager service.
🔧 Temporary Workarounds
Block SUM Servlet Access
linuxRestrict network access to the vulnerable Smart Update Manager servlet endpoint
# Add firewall rule to block /servlet/com.adventnet.me.opmanager.servlet.SumPDU
iptables -A INPUT -p tcp --dport 8060 -m string --string "SumPDU" --algo bm -j DROP
Disable SUM Servlet
linuxRemove or disable the vulnerable servlet from the web application
# Remove or rename the SumPDU servlet class file
mv /opt/ManageEngine/OpManager/webapps/ROOT/WEB-INF/classes/com/adventnet/me/opmanager/servlet/SumPDU.class /opt/ManageEngine/OpManager/webapps/ROOT/WEB-INF/classes/com/adventnet/me/opmanager/servlet/SumPDU.class.disabled
🧯 If You Can't Patch
- Isolate OpManager systems from internet and restrict internal network access
- Implement strict network segmentation and monitor for suspicious traffic to OpManager endpoints
🔍 How to Verify
Check if Vulnerable:
Check OpManager version in web interface (Help → About) or examine build number in installation directoryCheck Version:
grep -i 'build' /opt/ManageEngine/OpManager/conf/opmanager.confVerify Fix Applied:
Confirm version is Stable build 125203+ or Released build 125233+ and test that /servlet/com.adventnet.me.opmanager.servlet.SumPDU endpoint is no longer accessible or vulnerable📡 Detection & Monitoring
Log Indicators:
- Unusual requests to /servlet/com.adventnet.me.opmanager.servlet.SumPDU
- Java deserialization errors in application logs
- Unexpected process creation from OpManager service
Network Indicators:
- POST requests to /servlet/com.adventnet.me.opmanager.servlet.SumPDU with serialized Java objects
- Outbound connections from OpManager to suspicious IPs
SIEM Query:
source="opmanager.logs" AND (url="/servlet/com.adventnet.me.opmanager.servlet.SumPDU" OR "SumPDU")🔗 References
- http://packetstormsecurity.com/files/164231/ManageEngine-OpManager-SumPDU-Java-Deserialization.html
- https://www.manageengine.com/network-monitoring/help/read-me-complete.html#125203
- https://www.manageengine.com/network-monitoring/help/read-me-complete.html#125233
- http://packetstormsecurity.com/files/164231/ManageEngine-OpManager-SumPDU-Java-Deserialization.html
- https://www.manageengine.com/network-monitoring/help/read-me-complete.html#125203
- https://www.manageengine.com/network-monitoring/help/read-me-complete.html#125233
