CVE-2021-42077
📋 TL;DR
CVE-2021-42077 is a SQL injection vulnerability in PHP Event Calendar that allows attackers to execute arbitrary SQL commands through the username parameter in user_manager.php. This can lead to database compromise, data theft, and authentication bypass. Organizations using PHP Event Calendar before September 3, 2021 are affected.
💻 Affected Systems
- PHP Event Calendar Lite Edition
📦 What is this software?
Php Event Calendar by Kaysongroup
⚠️ Risk & Real-World Impact
Worst Case
Complete database compromise allowing data exfiltration, modification, or deletion; potential for remote code execution if database permissions allow; complete system takeover.
Likely Case
Data theft of user information, event data, and credentials; authentication bypass to gain administrative access; potential for lateral movement within the network.
If Mitigated
Limited to database read access if proper input validation and parameterized queries are implemented; contained impact if database runs with minimal privileges.
🎯 Exploit Status
Exploit requires network access to the vulnerable endpoint; SQL injection is well-documented with public proof-of-concept available.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Versions from 2021-09-03 onward
Vendor Advisory: https://www.syss.de/fileadmin/dokumente/Publikationen/Advisories/SYSS-2021-048.txt
Restart Required: No
Instructions:
1. Update PHP Event Calendar to version dated 2021-09-03 or later. 2. Replace vulnerable files with patched versions. 3. Verify the fix by testing the /server/ajax/user_manager.php endpoint.
🔧 Temporary Workarounds
Input Validation Filter
allImplement strict input validation for username parameter to reject SQL special characters
# In PHP code, add: if (preg_match('/[\'\"\\;\-]/', $username)) { die('Invalid input'); }
Web Application Firewall Rule
allBlock SQL injection patterns in requests to user_manager.php
# ModSecurity rule: SecRule ARGS:username "@detectSQLi" "id:1001,phase:2,deny,status:403"
🧯 If You Can't Patch
- Implement network segmentation to restrict access to the vulnerable endpoint
- Deploy a web application firewall with SQL injection detection rules
🔍 How to Verify
Check if Vulnerable:
Test the /server/ajax/user_manager.php endpoint with SQL injection payloads like: username=admin' OR '1'='1Check Version:
Check file modification dates or version metadata in PHP Event Calendar filesVerify Fix Applied:
Attempt SQL injection against patched endpoint; should return error or no database manipulation📡 Detection & Monitoring
Log Indicators:
- Unusual SQL errors in application logs
- Multiple failed login attempts with SQL patterns
- Requests to user_manager.php with special characters
Network Indicators:
- HTTP POST requests to /server/ajax/user_manager.php containing SQL keywords
- Unusual database query patterns from web server
SIEM Query:
source="web_logs" AND uri="/server/ajax/user_manager.php" AND (username="*'*" OR username="*;*" OR username="*--*")🔗 References
- http://packetstormsecurity.com/files/164777/PHP-Event-Calendar-Lite-Edition-SQL-Injection.html
- https://www.syss.de/fileadmin/dokumente/Publikationen/Advisories/SYSS-2021-048.txt
- http://packetstormsecurity.com/files/164777/PHP-Event-Calendar-Lite-Edition-SQL-Injection.html
- https://www.syss.de/fileadmin/dokumente/Publikationen/Advisories/SYSS-2021-048.txt
