CVE-2021-20110
📋 TL;DR
This vulnerability allows attackers to execute arbitrary code with SYSTEM privileges on ManageEngine Asset Explorer Agent installations by exploiting an integer overflow during HTTPS certificate validation. It affects Asset Explorer Agent version 1.0.34 and earlier. Attackers on the same network can impersonate the legitimate server to trigger the exploit.
💻 Affected Systems
- ManageEngine Asset Explorer Agent
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Full SYSTEM-level remote code execution on all vulnerable agents, allowing complete compromise of managed systems, data theft, and lateral movement.
Likely Case
Attacker gains SYSTEM privileges on vulnerable agent machines, enabling installation of malware, credential harvesting, and persistence mechanisms.
If Mitigated
If network segmentation and certificate validation are properly implemented, exploitation requires physical network access or compromise of internal systems first.
🎯 Exploit Status
Exploit requires network access to agent communication channel. Tenable's research includes technical details and exploitation methodology.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 1.0.35 or later
Vendor Advisory: https://www.manageengine.com/products/asset-explorer/sp-readme.html
Restart Required: Yes
Instructions:
1. Download Asset Explorer Agent version 1.0.35 or later from ManageEngine. 2. Deploy updated agent to all managed systems. 3. Restart agent service on all systems. 4. Verify agents are reporting with new version.
🔧 Temporary Workarounds
Network Segmentation
allIsolate Asset Explorer Agent traffic to prevent attackers from intercepting or spoofing server communications.
Certificate Pinning Enforcement
windowsConfigure agents to validate server certificates strictly and reject connections to untrusted servers.
🧯 If You Can't Patch
- Implement strict network segmentation to isolate Asset Explorer Agent traffic from untrusted networks
- Deploy host-based firewalls to restrict agent communication to authorized management servers only
🔍 How to Verify
Check if Vulnerable:
Check agent version in Asset Explorer console or examine agent executable version on endpoints. Version 1.0.34 or earlier is vulnerable.Check Version:
On Windows: Check file version of AEClient.exe or examine registry at HKLM\SOFTWARE\ManageEngine\AssetExplorer\AgentVerify Fix Applied:
Confirm agent version is 1.0.35 or later in Asset Explorer management console and verify agents are communicating successfully.📡 Detection & Monitoring
Log Indicators:
- Unusual network connections to agent port (typically 80/443)
- Failed certificate validation attempts
- Process creation from agent executable with unusual parameters
Network Indicators:
- NEWSCAN requests from unauthorized IP addresses
- Large Content-Length headers (1073741823+) in POST requests to agents
- Spoofed server IP addresses communicating with agents
SIEM Query:
source="agent_logs" AND (content_length>=1073741823 OR dest_ip!=authorized_server_ip)