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Vulnerability record · CVE-2026-40308 · published 16 April 2026

CVE-2026-40308: Insecure direct object reference vulnerability

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.

8.8 CVSS 4.0 High EPSS 1.1% · top 34.8% CWE-639 · Insecure direct object reference Deferred
8.8CVSS 4.0 base score
1.1%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
3References
17 Jun 2026Last modified by NVD

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.

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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:

References

LinkTags
https://github.com/joedolson/my-calendar/releases/tag/v3.7.7
https://github.com/joedolson/my-calendar/security/advisories/GHSA-2mvx-f5qm-v2ch
https://github.com/joedolson/my-calendar/security/advisories/GHSA-2mvx-f5qm-v2ch

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

8.4CVE-2026-55255Langflow IDOR in responses endpoint allows cross-user flow executionLangflow before 1.9.1 has an insecure direct object reference in the /api/v1/responses endpoint. An authenticated attacker can supply another user's …KEVEPSS 0.89%analysed

Source: NIST National Vulnerability Database (record CVE-2026-40308), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.