CVE-2020-7864
📋 TL;DR
CVE-2020-7864 is an authentication bypass vulnerability in Raonwiz DEXT5Editor that allows attackers to upload and execute arbitrary files through parameter manipulation. This leads to remote code execution on affected systems. Organizations using DEXT5Editor versions prior to 3.5.1405747.1100.03 are at risk.
💻 Affected Systems
- Raonwiz DEXT5Editor
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Full system compromise with attacker gaining complete control over the server, data exfiltration, ransomware deployment, and lateral movement to other systems.
Likely Case
Webshell upload leading to persistent backdoor access, data theft, and further exploitation of the compromised server.
If Mitigated
Attack prevented at web application firewall level or blocked by file upload restrictions, resulting in failed exploitation attempts.
🎯 Exploit Status
Authentication bypass via parameter manipulation makes exploitation straightforward. Public exploit details exist in Korean CERT advisories.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 3.5.1405747.1100.03 or later
Vendor Advisory: https://www.krcert.or.kr/krcert/secNoticeView.do?bulletin_writing_sequence=36085
Restart Required: Yes
Instructions:
1. Download latest DEXT5Editor version from official vendor. 2. Backup current installation. 3. Install updated version. 4. Restart web application/service. 5. Verify functionality.
🔧 Temporary Workarounds
Web Application Firewall Rules
allImplement WAF rules to block parameter manipulation attempts and file uploads to DEXT5Editor endpoints.
WAF-specific rules to block: POST requests containing 'DEXT5' parameters with suspicious values
Block file uploads to known DEXT5Editor upload paths
File Upload Restrictions
linuxConfigure web server to block execution of uploaded files in DEXT5Editor directories.
For Apache: <Location /dext5/upload/>\n php_flag engine off\n RemoveHandler .php .phtml .php3 .php4 .php5 .php7\n RemoveType .php .phtml .php3 .php4 .php5 .php7\n</Location>
For Nginx: location ~* ^/dext5/upload/.+\.(php|phtml|php[3457])$ { deny all; }
🧯 If You Can't Patch
- Network segmentation: Isolate DEXT5Editor servers from critical systems and restrict outbound connections.
- Implement strict file upload validation: Allow only specific file types and scan all uploads with antivirus.
🔍 How to Verify
Check if Vulnerable:
Check DEXT5Editor version in web interface or configuration files. If version is below 3.5.1405747.1100.03, system is vulnerable.Check Version:
Check web interface or examine DEXT5Editor installation directory for version information files.Verify Fix Applied:
Confirm version is 3.5.1405747.1100.03 or higher. Test file upload functionality with parameter manipulation attempts - should be blocked.📡 Detection & Monitoring
Log Indicators:
- Multiple failed file upload attempts to DEXT5Editor endpoints
- Unusual parameter values in POST requests to DEXT5Editor
- Execution of unexpected files in upload directories
Network Indicators:
- POST requests with manipulated parameters to /dext5/upload/ paths
- Outbound connections from web server following file uploads
SIEM Query:
source="web_server" AND (uri_path="/dext5/upload/" OR user_agent CONTAINS "DEXT5") AND (status_code=200 OR parameter CONTAINS suspicious_pattern)