CVE-2020-18662
📋 TL;DR
This CVE describes a SQL injection vulnerability in gnuboard5's installation script that allows attackers to execute arbitrary SQL commands via the table_prefix parameter. It affects gnuboard5 installations up to version 5.3.2.8 during the installation process. Attackers can exploit this to compromise the database and potentially gain control of the application.
💻 Affected Systems
- gnuboard5
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete database compromise allowing data theft, data manipulation, and potential remote code execution through database functions.
Likely Case
Database information disclosure, privilege escalation, and installation of backdoors in the gnuboard5 system.
If Mitigated
No impact if installation is completed and vulnerable file removed, or if input validation prevents exploitation.
🎯 Exploit Status
Simple SQL injection via GET/POST parameter. Exploitation requires access to install_db.php during installation phase.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: v5.3.2.9 and later
Vendor Advisory: https://github.com/gnuboard/gnuboard5/issues/43
Restart Required: No
Instructions:
1. Upgrade gnuboard5 to version 5.3.2.9 or later. 2. Delete install_db.php after installation if still present. 3. Verify the fix by checking that table_prefix parameter is properly sanitized.
🔧 Temporary Workarounds
Remove installation script
linuxDelete or restrict access to install_db.php after installation completes
rm -f install_db.php
chmod 000 install_db.php
Input validation workaround
allAdd parameter validation to table_prefix input before database operations
Edit install_db.php to add: if(!preg_match('/^[a-zA-Z0-9_]+$/', $table_prefix)) { die('Invalid table prefix'); }
🧯 If You Can't Patch
- Ensure install_db.php is deleted or inaccessible after installation completes
- Implement web application firewall rules to block SQL injection patterns targeting the table_prefix parameter
🔍 How to Verify
Check if Vulnerable:
Check if install_db.php exists and is accessible, and gnuboard5 version is <= 5.3.2.8Check Version:
Check config.php or common.php for version information, or use: grep -r 'G5_VERSION' .Verify Fix Applied:
Verify gnuboard5 version is >= 5.3.2.9 and install_db.php is either patched or removed📡 Detection & Monitoring
Log Indicators:
- Unusual SQL queries during installation
- Multiple requests to install_db.php with SQL-like parameters
- Database errors containing SQL syntax
Network Indicators:
- HTTP requests to install_db.php with SQL injection payloads in table_prefix parameter
- Unusual database connections from web server
SIEM Query:
source="web_logs" AND uri="/install_db.php" AND (table_prefix CONTAINS "'" OR table_prefix CONTAINS "--" OR table_prefix CONTAINS ";")🔗 References
- https://github.com/LoRexxar/CVE_Request/tree/master/gnuboard5%20mul%20vuls%20before%20v5.3.2.8#sql-injection-in-install_dbphp
- https://github.com/gnuboard/gnuboard5/issues/43
- https://www.seebug.org/vuldb/ssvid-97927
- https://github.com/LoRexxar/CVE_Request/tree/master/gnuboard5%20mul%20vuls%20before%20v5.3.2.8#sql-injection-in-install_dbphp
- https://github.com/gnuboard/gnuboard5/issues/43
- https://www.seebug.org/vuldb/ssvid-97927
