CVE-2026-40308

8.8 HIGH 0.9% exploit odds Fix listed Auth & access Web app

What it is

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.

At a glance

Exploitability: Can be exploited over the network without logging in. High risk of data exposure, service disruption.
Exploit odds: 0.9% chance of exploitation in the next 30 days (EPSS).
Fix: A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

2026-04-16 22:16 UTC PublishedDisclosed publicly on CVE.org and NVD
2026-06-17 10:44 UTC Last updatedMost recent change to the record

Why it ranks here

Exploited in the wild: no, CISA does not list it.
Exploit odds: 0.9% in the next 30 days (EPSS).
Severity: 8.8 HIGH (CVSS).
Fix: a patch or advisory is linked.

Details

Published: 2026-04-16 22:16 UTC
Last modified: 2026-06-17 10:44 UTC
Exploit probability: 0.9% · EPSS, next 30 days
Weakness: CWE-639 · Insecure direct object reference
Record status: Deferred

Attack profile CVSS 4.0 · 8.8

Attack vector: Network
Complexity: Low
Attack requirements: None
Privileges needed: None
User interaction: None
Confidentiality: High
Integrity: None
Availability: High

Raw 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/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:X/V:X/RE:X/U:X

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2026-40308.md and follow it. Check whether this project is affected by CVE-2026-40308. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

· More options · Status badge

Download Square Reddit

Fix and advisories

References

NVD record · CVE.org record