CVE-2021-40543
📋 TL;DR
This vulnerability allows attackers to execute arbitrary SQL commands on Opensis-Classic Version 8.0 by injecting malicious input into the 'usrid' and 'prof_id' parameters in PasswordCheck.php. It affects all users running the vulnerable version, potentially leading to unauthorized data access or system compromise.
💻 Affected Systems
- Opensis-Classic
📦 What is this software?
Opensis by Os4ed
⚠️ Risk & Real-World Impact
Worst Case
Full database compromise, including data theft, modification, or deletion, and potential remote code execution leading to complete system takeover.
Likely Case
Unauthorized access to sensitive user data, such as passwords or personal information, and potential privilege escalation.
If Mitigated
Limited impact if input validation and parameterized queries are enforced, preventing SQL injection but still exposing system to other attacks if not fully patched.
🎯 Exploit Status
Exploitation is straightforward via crafted HTTP requests, and public references indicate proof-of-concept details are available.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check vendor for updates beyond Version 8.0, as the issue was reported via GitHub issues.
Vendor Advisory: https://github.com/OS4ED/openSIS-Classic/issues/191
Restart Required: No
Instructions:
1. Update to the latest version of Opensis-Classic from the official repository. 2. Apply any security patches provided by the vendor. 3. Review and sanitize all user inputs in the application code.
🔧 Temporary Workarounds
Input Validation and Sanitization
allImplement server-side validation to sanitize 'usrid' and 'prof_id' parameters, rejecting malicious input.
Modify PasswordCheck.php to use prepared statements or escape special characters in SQL queries.
Web Application Firewall (WAF) Rules
allDeploy a WAF to block SQL injection patterns targeting the vulnerable parameters.
Configure WAF rules to filter requests containing SQL keywords in 'usrid' or 'prof_id' parameters.
🧯 If You Can't Patch
- Restrict access to the vulnerable endpoint by implementing IP whitelisting or authentication requirements.
- Monitor and log all access to PasswordCheck.php for suspicious activity and review logs regularly.
🔍 How to Verify
Check if Vulnerable:
Test by sending a crafted HTTP GET request to PasswordCheck.php with SQL injection payloads in 'usrid' or 'prof_id' parameters and observe database errors or unexpected behavior.Check Version:
Check the software version via the application interface or configuration files; for Opensis-Classic, review version metadata in installation directories.Verify Fix Applied:
After patching, repeat the test to ensure no SQL errors occur and the application handles input securely.📡 Detection & Monitoring
Log Indicators:
- Unusual SQL error messages in application logs, multiple failed login attempts, or requests with suspicious strings in 'usrid' or 'prof_id' parameters.
Network Indicators:
- HTTP requests containing SQL keywords (e.g., UNION, SELECT, DROP) in query parameters directed at PasswordCheck.php.
SIEM Query:
Example: search for 'PasswordCheck.php' AND ('usrid' OR 'prof_id') AND ('SQL' OR 'error' OR 'injection') in web server logs.