CVE-2021-24943
📋 TL;DR
This vulnerability allows unauthenticated attackers to execute arbitrary SQL commands on WordPress sites running vulnerable versions of the Registrations for the Events Calendar plugin. Attackers can potentially access, modify, or delete database content, including sensitive user data. All WordPress sites with the vulnerable plugin installed are affected.
💻 Affected Systems
- Registrations for the Events Calendar WordPress Plugin
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete database compromise leading to data theft, privilege escalation, site takeover, or remote code execution via SQL injection.
Likely Case
Data exfiltration of user information, plugin/theme manipulation, or site defacement.
If Mitigated
Limited impact if proper WAF rules, input validation, and database permissions are in place.
🎯 Exploit Status
Simple SQL injection via AJAX endpoint with no authentication required. Public exploit scripts are available.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 2.7.6
Vendor Advisory: https://wpscan.com/vulnerability/ba50c590-42ee-4523-8aa0-87ac644b77ed
Restart Required: No
Instructions:
1. Log into WordPress admin panel. 2. Navigate to Plugins > Installed Plugins. 3. Find 'Registrations for the Events Calendar'. 4. Click 'Update Now' if update is available. 5. If no update appears, manually download version 2.7.6+ from WordPress repository.
🔧 Temporary Workarounds
Disable vulnerable AJAX endpoint
allBlock access to the rtec_send_unregister_link AJAX action via .htaccess or web application firewall.
# Add to .htaccess:
RewriteCond %{QUERY_STRING} action=rtec_send_unregister_link [NC]
RewriteRule .* - [F,L]
🧯 If You Can't Patch
- Disable or uninstall the Registrations for the Events Calendar plugin immediately.
- Implement strict WAF rules to block SQL injection patterns targeting the vulnerable endpoint.
🔍 How to Verify
Check if Vulnerable:
Check WordPress admin panel > Plugins > Installed Plugins for 'Registrations for the Events Calendar' version number.Check Version:
wp plugin list --name='registrations-for-the-events-calendar' --field=versionVerify Fix Applied:
Confirm plugin version is 2.7.6 or higher in WordPress admin panel.📡 Detection & Monitoring
Log Indicators:
- Unusual POST requests to /wp-admin/admin-ajax.php with action=rtec_send_unregister_link containing SQL syntax
Network Indicators:
- SQL error messages in HTTP responses, unusual database query patterns
SIEM Query:
source="web_logs" AND uri="/wp-admin/admin-ajax.php" AND query="*action=rtec_send_unregister_link*" AND (query="*UNION*" OR query="*SELECT*" OR query="*INSERT*" OR query="*DELETE*")