CVE-2023-2796: EventON WordPress Auth Bypass Vulnerability

CVE-2023-2796 Overview

CVE-2023-2796 is an Insecure Direct Object Reference (IDOR) vulnerability affecting the EventON WordPress plugin. The vulnerability exists due to missing authentication and authorization controls in the eventon_ics_download AJAX action, allowing unauthenticated visitors to access private and password-protected Events by guessing their numeric IDs. This flaw enables unauthorized information disclosure of potentially sensitive event data that site administrators intended to keep restricted.

Critical Impact

Unauthenticated attackers can enumerate and access private event data by iterating through numeric IDs, bypassing access controls entirely.

Affected Products

• EventON WordPress Plugin versions before 2.1.2
• WordPress installations running vulnerable EventON versions
• Sites using EventON for private or password-protected event management

Discovery Timeline

• 2023-07-10 - CVE-2023-2796 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2023-2796

Vulnerability Analysis

This vulnerability is classified under CWE-862 (Missing Authorization), representing a failure to enforce proper access control mechanisms. The EventON plugin exposes an AJAX endpoint (eventon_ics_download) that processes requests to download ICS calendar files for events. However, this endpoint lacks both authentication checks (verifying user identity) and authorization checks (verifying user permissions), creating a significant access control gap.

The attack surface is network-accessible and requires no authentication or user interaction, making exploitation straightforward. While the vulnerability only results in information disclosure (read-only access to protected data), the high EPSS score of 77.5% indicates this vulnerability is highly likely to be exploited in the wild.

Root Cause

The root cause is the absence of authentication and authorization validation in the eventon_ics_download AJAX handler. WordPress AJAX actions should implement check_ajax_referer() for nonce verification and current_user_can() for capability checks. The vulnerable code path processes event ID parameters and returns ICS data without verifying whether the requesting user has permission to access private or password-protected events.

Attack Vector

The attack vector leverages the predictable nature of WordPress post IDs, which are sequential integers. An attacker can exploit this vulnerability through the following mechanism:

1. The attacker identifies the AJAX endpoint URL: wp-admin/admin-ajax.php?action=eventon_ics_download
2. The attacker iterates through numeric event IDs by modifying the request parameter
3. For each valid event ID, the server returns the ICS calendar data regardless of the event's visibility settings
4. The attacker can systematically enumerate all events, including those marked as private or protected with passwords

This enumeration attack requires minimal technical skill and can be easily automated with simple scripts or tools like Burp Suite Intruder to iterate through ID ranges.

Detection Methods for CVE-2023-2796

Indicators of Compromise

• Unusual spikes in requests to admin-ajax.php with the action=eventon_ics_download parameter
• Sequential or enumerated event ID values in request logs from single IP addresses
• Elevated access patterns to ICS download functionality from unauthenticated users
• Automated traffic patterns with rapidly incrementing numeric parameters

Detection Strategies

• Monitor web server access logs for repeated requests to the EventON ICS download AJAX action
• Implement Web Application Firewall (WAF) rules to detect sequential parameter enumeration attempts
• Configure alerting for high-volume requests to admin-ajax.php from single sources
• Use WordPress security plugins to audit AJAX action access patterns

Monitoring Recommendations

• Enable verbose logging for WordPress AJAX requests in your web server configuration
• Deploy real-time log analysis to identify enumeration attack patterns
• Implement rate limiting on AJAX endpoints to slow enumeration attempts
• Review access logs regularly for suspicious activity targeting EventON endpoints

How to Mitigate CVE-2023-2796

Immediate Actions Required

• Update the EventON plugin to version 2.1.2 or later immediately
• Audit access logs for evidence of exploitation prior to patching
• Review private and password-protected events for potential data exposure
• Consider temporarily disabling the EventON plugin if immediate patching is not possible

Patch Information

The vulnerability is resolved in EventON version 2.1.2 and later. Site administrators should update through the WordPress plugin update mechanism or by manually downloading the patched version from the plugin vendor. After updating, verify the plugin version in the WordPress admin panel under Plugins.

For additional technical details, refer to the WPScan Vulnerability Report and the Packet Storm Exploit Report.

Workarounds

• Implement WAF rules to block unauthenticated requests to the eventon_ics_download AJAX action
• Use WordPress security plugins to add authentication requirements to vulnerable endpoints
• Restrict access to admin-ajax.php for specific actions through server-side configuration
• Consider moving sensitive events to alternative solutions until the patch can be applied

# Example Apache .htaccess rule to restrict access to the vulnerable AJAX action
# Add to WordPress root .htaccess file as a temporary mitigation
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteCond %{QUERY_STRING} action=eventon_ics_download [NC]
RewriteCond %{HTTP_COOKIE} !wordpress_logged_in [NC]
RewriteRule ^wp-admin/admin-ajax\.php$ - [F,L]
</IfModule>