CVE-2021-36741
📋 TL;DR
This vulnerability allows authenticated attackers to upload arbitrary files to Trend Micro security products due to improper input validation. Attackers must first obtain management console credentials to exploit this flaw. Affected products include Apex One, OfficeScan XG, and Worry-Free Business Security.
💻 Affected Systems
- Trend Micro Apex One
- Trend Micro Apex One as a Service
- Trend Micro OfficeScan XG
- Trend Micro Worry-Free Business Security
📦 What is this software?
Apex One by Trendmicro
Officescan by Trendmicro
⚠️ Risk & Real-World Impact
Worst Case
Full system compromise through remote code execution, data exfiltration, or ransomware deployment via malicious file uploads.
Likely Case
Malware deployment, persistence establishment, or lateral movement within the network using uploaded malicious files.
If Mitigated
Limited impact due to strong authentication controls, network segmentation, and file upload restrictions.
🎯 Exploit Status
Exploitation requires valid credentials but is straightforward once authenticated. No public exploit code available.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Apply latest security patches from Trend Micro
Vendor Advisory: https://success.trendmicro.com/solution/000287819
Restart Required: Yes
Instructions:
1. Log into Trend Micro management console
2. Navigate to Update section
3. Download and apply latest security patches
4. Restart affected services as prompted
🔧 Temporary Workarounds
Restrict Management Console Access
allLimit access to Trend Micro management console to trusted IP addresses only
Configure firewall rules to restrict access to management console ports (typically 4343, 8443)
Strengthen Authentication
windowsEnforce strong passwords and multi-factor authentication for management console accounts
Enable MFA in Trend Micro console: Settings > Security > Authentication
🧯 If You Can't Patch
- Implement strict network segmentation to isolate Trend Micro management interfaces
- Monitor for unusual file upload activities and failed authentication attempts
🔍 How to Verify
Check if Vulnerable:
Check product version in Trend Micro management console under Help > AboutCheck Version:
In Trend Micro console: Help > About shows current versionVerify Fix Applied:
Verify patch installation in Update History and confirm version is patched📡 Detection & Monitoring
Log Indicators:
- Unusual file upload activities in Trend Micro logs
- Multiple failed authentication attempts followed by successful login
- Suspicious file creation in unexpected directories
Network Indicators:
- Unusual traffic to management console ports from unexpected sources
- Large file uploads to Trend Micro management interfaces
SIEM Query:
source="trendmicro" AND (event_type="file_upload" OR auth_failure>3)🔗 References
- https://success.trendmicro.com/jp/solution/000287796
- https://success.trendmicro.com/jp/solution/000287815
- https://success.trendmicro.com/solution/000287819
- https://success.trendmicro.com/solution/000287820
- https://success.trendmicro.com/jp/solution/000287796
- https://success.trendmicro.com/jp/solution/000287815
- https://success.trendmicro.com/solution/000287819
- https://success.trendmicro.com/solution/000287820
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-36741
