CVE-2021-31520
📋 TL;DR
CVE-2021-31520 is a session token authentication bypass vulnerability in Trend Micro IM Security that allows remote attackers to guess administrators' session tokens. This enables unauthorized access to the web management interface, potentially leading to full system compromise. Affected systems include Trend Micro IM Security versions 1.6 and 1.6.5.
💻 Affected Systems
- Trend Micro IM Security
📦 What is this software?
Im Security by Trendmicro
Im Security by Trendmicro
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of the IM Security management interface, allowing attackers to disable security controls, exfiltrate sensitive data, and use the system as a foothold for further network attacks.
Likely Case
Unauthorized administrative access leading to configuration changes, security policy modification, and potential data exposure.
If Mitigated
Limited impact with proper network segmentation and access controls, though the vulnerability still exists.
🎯 Exploit Status
The vulnerability involves predictable/weak session tokens that can be brute-forced or guessed.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 1.6.5-hotfix-2903 or later
Vendor Advisory: https://success.trendmicro.com/solution/000286439
Restart Required: Yes
Instructions:
1. Download the hotfix from Trend Micro support portal. 2. Backup current configuration. 3. Apply the hotfix following vendor instructions. 4. Restart the IM Security service. 5. Verify the fix by checking version.
🔧 Temporary Workarounds
Network Access Restriction
allRestrict access to the IM Security management interface to trusted IP addresses only.
# Configure firewall rules to allow only specific IPs to access management port
# Example: iptables -A INPUT -p tcp --dport [management_port] -s [trusted_ip] -j ACCEPT
# Example: iptables -A INPUT -p tcp --dport [management_port] -j DROP
🧯 If You Can't Patch
- Implement strict network segmentation to isolate the IM Security management interface
- Enable multi-factor authentication if supported and monitor for unauthorized access attempts
🔍 How to Verify
Check if Vulnerable:
Check the IM Security version via web interface or command line. If version is 1.6 or 1.6.5 without hotfix-2903, the system is vulnerable.Check Version:
# On Linux: cat /opt/trendmicro/imsecurity/version.txt
# On Windows: Check via IM Security web interface or installation directoryVerify Fix Applied:
Verify the version shows 1.6.5-hotfix-2903 or later. Test that session tokens are now properly randomized and not predictable.📡 Detection & Monitoring
Log Indicators:
- Multiple failed login attempts followed by successful login from unusual IP
- Administrative actions from unexpected IP addresses
- Session token brute force patterns in access logs
Network Indicators:
- Unusual traffic patterns to management interface port
- Multiple sequential requests to session endpoints
SIEM Query:
source="imsecurity.log" ("authentication failed" OR "login failed") count by src_ip > 10 within 5m