Vulnerability · Published Apr 16, 2026 · Assigned by GitHub_M
CVE-2026-40308My Calendar: Unauthenticated Information Disclosure (IDOR) via Multisite switch_to_blog
High 8.8
In plain English
A high-severity authorization bypass via user-controlled key in my-calendar from joedolson. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.9% (higher than 61% of all known vulnerabilities). Ready-made attack tooling exists: Nuclei. Fixed versions are available - upgrade the affected package.
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Packagist | joedolson/my-calendar | 3.7.7 | GHSA-2mvx-f5qm-v2ch |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| joedolson | my-calendar | < 3.7.7 |
Weakness: CWE-639 · Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:H/SC:N/SI:N/SA:N
References
- https://github.com/joedolson/my-calendar/security/advisories/GHSA-2mvx-f5qm-v2ch x_refsource_CONFIRM
- https://github.com/joedolson/my-calendar/releases/tag/v3.7.7 x_refsource_MISC