CVE-2021-39377
📋 TL;DR
This SQL injection vulnerability in openSIS 8.0 allows attackers to execute arbitrary SQL commands through the username parameter in index.php when using MySQL/MariaDB. This can lead to unauthorized data access, modification, or deletion. All openSIS 8.0 installations using MySQL/MariaDB are affected.
💻 Affected Systems
- openSIS Classic
📦 What is this software?
Opensis by Os4ed
⚠️ Risk & Real-World Impact
Worst Case
Complete database compromise including data theft, data destruction, privilege escalation to admin, and potential remote code execution via database functions.
Likely Case
Unauthorized access to sensitive student and staff data, grade manipulation, and administrative privilege escalation.
If Mitigated
Limited impact with proper input validation and parameterized queries preventing SQL injection.
🎯 Exploit Status
Exploitation requires no authentication and simple SQL injection payloads work against the username parameter.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 8.1 or later
Vendor Advisory: https://github.com/OS4ED/openSIS-Classic
Restart Required: No
Instructions:
1. Backup your database and application files. 2. Download openSIS 8.1 or later from GitHub. 3. Replace vulnerable index.php and related files. 4. Test the application functionality.
🔧 Temporary Workarounds
Web Application Firewall (WAF)
allDeploy a WAF with SQL injection protection rules to block malicious requests.
Input Validation Filter
linuxAdd server-side input validation to reject SQL special characters in username parameter.
Example PHP: if (preg_match('/[\'\"\;\-\-]/', $_POST['username'])) { die('Invalid input'); }
🧯 If You Can't Patch
- Isolate the openSIS server behind a firewall with strict access controls.
- Implement database user privilege separation with minimal required permissions.
🔍 How to Verify
Check if Vulnerable:
Test with SQL injection payload in username field: ' OR '1'='1Check Version:
Check openSIS version in admin panel or review index.php file headers.Verify Fix Applied:
Attempt SQL injection payloads and verify they are rejected or properly escaped.📡 Detection & Monitoring
Log Indicators:
- Multiple failed login attempts with SQL keywords in username field
- Unusual database query patterns from web server IP
Network Indicators:
- HTTP POST requests to index.php containing SQL injection patterns
SIEM Query:
source="web_logs" AND uri="/index.php" AND (username="*' OR*" OR username="*--*" OR username="*;*")