CVE-2020-7877
📋 TL;DR
CVE-2020-7877 is a buffer overflow vulnerability in ZOOK remote administration tool that allows attackers to execute arbitrary commands by sending a specially crafted OUTERIP value in the 'ConnectMe' command. This affects organizations using ZOOK solution for remote administration. The vulnerability exists due to missing boundary checks during command parsing.
💻 Affected Systems
- ZOOK Remote Administration Tool
📦 What is this software?
Zook Agent by Mastersoft
Zook Viewer by Mastersoft
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with attacker gaining full control over affected systems, enabling data theft, ransomware deployment, or persistent backdoor installation.
Likely Case
Remote code execution leading to unauthorized access, data exfiltration, and lateral movement within the network.
If Mitigated
Limited impact if proper network segmentation, least privilege, and monitoring are in place, potentially containing the attack to isolated segments.
🎯 Exploit Status
Exploitation requires network access to the ZOOK service and knowledge of the ConnectMe command structure. The buffer overflow mechanism is straightforward once the protocol is understood.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Not specified in available references - check vendor for latest version
Vendor Advisory: https://www.boho.or.kr/krcert/secNoticeView.do?bulletin_writing_sequence=36216
Restart Required: Yes
Instructions:
1. Contact ZOOK vendor for patched version. 2. Backup configuration and data. 3. Install updated version. 4. Restart ZOOK services. 5. Verify functionality.
🔧 Temporary Workarounds
Network Access Restriction
allRestrict network access to ZOOK administration interface to trusted IP addresses only
# Example firewall rule (Linux): iptables -A INPUT -p tcp --dport [ZOOK_PORT] -s [TRUSTED_IP] -j ACCEPT
# Windows Firewall: New-NetFirewallRule -DisplayName "ZOOK Access" -Direction Inbound -Protocol TCP -LocalPort [ZOOK_PORT] -RemoteAddress [TRUSTED_IP] -Action Allow
Disable Remote Administration
allTemporarily disable ZOOK remote administration features if not critically needed
# Check ZOOK configuration for remote administration settings
# Disable in configuration file or administration interface
🧯 If You Can't Patch
- Implement strict network segmentation to isolate ZOOK systems from critical assets
- Deploy host-based intrusion detection and monitor for unusual process creation or network connections from ZOOK
🔍 How to Verify
Check if Vulnerable:
Check ZOOK version against vendor advisory. If running any version before the patched release, assume vulnerable.Check Version:
# Check ZOOK version through administration interface or configuration filesVerify Fix Applied:
Verify ZOOK version matches patched version from vendor. Test ConnectMe functionality with normal operations.📡 Detection & Monitoring
Log Indicators:
- Unusual ConnectMe command patterns
- Multiple failed connection attempts to ZOOK service
- Process creation from ZOOK service with unusual parameters
Network Indicators:
- Unusual network traffic to ZOOK service port
- Multiple connection attempts from single source
- Large OUTERIP parameter values in network captures
SIEM Query:
source="ZOOK" AND (event_type="ConnectMe" AND parameter_size>normal_threshold) OR (process_name=unusual_executable AND parent_process="ZOOK")