CVE-2026-40308 PoC — My Calendar: Unauthenticated Information Disclosure (IDOR) via Multisite switch_to_blog

Source

https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2026/CVE-2026-40308.yaml

Associated Vulnerability

Title:My Calendar: Unauthenticated Information Disclosure (IDOR) via Multisite switch_to_blog (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.

Description

My Calendar WordPress plugin <= 3.7.6 contains an injection vulnerability caused by unvalidated user input passed to parse_str() in mc_ajax_mcjs_action endpoint, letting unauthenticated attackers access or crash sites via switch_to_blog(), exploit requires WordPress Multisite or Single Site setup.

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