My-calendar - Information Disclosure (CVE-2026-40308)
Description
My Calendar is a WordPress plugin for managing calendar events. In versions 3.7.6 and below, the mc_ajax_mcjs_action AJAX endpoint, registered for unauthenticated users, passes user-supplied arguments through parse_str() without validation, allowing injection of arbitrary parameters including a site value. On WordPress Multisite installations, this enables an unauthenticated attacker to call switch_to_blog() with an arbitrary site ID and extract calendar events from any sub-site on the network, including private or hidden events. On standard Single Site installations, switch_to_blog() does not exist, causing an uncaught PHP fatal error and crashing the worker thread, creating an unauthenticated denial of service vector. This issue has been fixed in version 3.7.7.
psychologyCrowdSec Analysis
CVE-2026-40308 is an information disclosure vulnerability in the My Calendar WordPress plugin versions 3.7.6 and below. This flaw allows unauthenticated attackers to exploit the mc_ajax_mcjs_action AJAX endpoint to inject arbitrary parameters, enabling them to access calendar events—including private or hidden ones—across any sub-site in a WordPress Multisite network. On single-site installations, the vulnerability can be leveraged to crash the worker thread, resulting in a denial of service. This issue has been addressed in version 3.7.7.
CrowdSec has been tracking this vulnerability and its exploits since 6th of May 2026.
CrowdSec has not observed any significant exploitation activity targeting CVE-2026-40308 across its network. As a result, no community-driven trend analysis is available for this vulnerability at this time.
Attackers exploit the /wp-admin/admin-ajax.php endpoint with the action=mcjs_action parameter to trigger information disclosure or denial of service in vulnerable My Calendar WordPress plugin installations.
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| Event | Date |
|---|---|
| CVE Published | 2026-04-16 |
| Rule Released | 2026-05-06 |
| CrowdSec First Seen | 2026-08-19 |