CVE-2021-37926
📋 TL;DR
CVE-2021-37926 is a critical unrestricted file upload vulnerability in Zoho ManageEngine ADManager Plus that allows attackers to upload malicious files and execute arbitrary code remotely. This affects all organizations running ADManager Plus version 7110 and earlier. Attackers can gain complete control of affected systems.
💻 Affected Systems
- Zoho ManageEngine ADManager Plus
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Full system compromise leading to domain takeover, data exfiltration, ransomware deployment, and lateral movement across the network.
Likely Case
Remote code execution leading to backdoor installation, credential theft, and persistence on the compromised system.
If Mitigated
Limited impact with proper network segmentation, but still potential for initial foothold in the environment.
🎯 Exploit Status
Multiple public exploits exist, and this vulnerability has been actively exploited in the wild. No authentication required for exploitation.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 7111 and later
Vendor Advisory: https://www.manageengine.com/products/ad-manager/release-notes.html#7111
Restart Required: Yes
Instructions:
1. Download ADManager Plus version 7111 or later from ManageEngine website. 2. Stop the ADManager Plus service. 3. Run the installer/upgrade package. 4. Restart the service. 5. Verify the version is 7111 or higher.
🔧 Temporary Workarounds
Network Access Restriction
allRestrict network access to ADManager Plus to only trusted IP addresses and networks.
Use firewall rules to limit access: iptables -A INPUT -p tcp --dport 8383 -s trusted_network -j ACCEPT
iptables -A INPUT -p tcp --dport 8383 -j DROP
Web Application Firewall
allDeploy WAF rules to block file upload attempts to vulnerable endpoints.
Configure WAF to block requests containing file upload patterns to /servlet/* endpoints
🧯 If You Can't Patch
- Immediately isolate the ADManager Plus server from the internet and restrict internal network access
- Implement strict file upload validation and monitoring on the application server
🔍 How to Verify
Check if Vulnerable:
Check the ADManager Plus version in the web interface or installation directory. Versions 7110 and below are vulnerable.Check Version:
On Windows: Check 'C:\Program Files\ManageEngine\ADManager Plus\conf\version.txt' or web interface. On Linux: Check '/opt/ManageEngine/ADManager Plus/conf/version.txt'Verify Fix Applied:
Verify the version shows 7111 or higher in the web interface or via the version check command.📡 Detection & Monitoring
Log Indicators:
- Unusual file uploads to /servlet/* endpoints
- Unexpected process creation from ADManager Plus service
- Large file uploads with suspicious extensions (.jsp, .war, .exe)
Network Indicators:
- HTTP POST requests to /servlet/UploadFileServlet with file uploads
- Outbound connections from ADManager Plus server to unknown external IPs
SIEM Query:
source="ADManager Plus" AND (uri_path="/servlet/UploadFileServlet" OR process_name="cmd.exe" OR process_name="powershell.exe")