CVE-2026-104798

9.8Critical

Published 16 Oct 2026 · NVD status: Deferred · AI triage by gemini-3.8-flash

9.8Critical

Attack vector: Network
Complexity: Low
Privileges needed: None
User interaction: None
Impact: Full C/I/A compromise
Weakness: CWE-269

Impact

Unauthenticated remote attackers can take over the primary administrator account (user ID 1) and gain full wp-admin access. They only need network access to the default, publicly exposed /my-calendar/ page.

Root cause

The plugin reflects the unsanitized `mcs` GET parameter into post content before shortcodes are parsed, allowing injected shortcodes to pass arbitrary functions directly into `call_user_func()`.

Affected systems

My Calendar – Accessible Event Manager plugin for WordPress versions up to and including 3.8.7.

CVSS v3.1 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Fix & remediation

Upgrade the My Calendar plugin to a version newer than 3.8.7, or deactivate the plugin immediately until patched.

shell

$ wp plugin update my-calendar

AI-suggested. Run it in staging first and check it against the vendor advisory. Why?

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NVD description

The My Calendar – Accessible Event Manager plugin for WordPress is vulnerable to Privilege Escalation in all versions up to, and including, 3.8.7. The public `mcs` GET parameter is reflected into post content unsanitized before WordPress core's `do_shortcode` filter runs, allowing an unauthenticated attacker to inject a nested `[my_calendar above=...]` shortcode; `mc_generate_calendar_nav()` then splits the `above` attribute on commas and dispatches each element via `call_user_func()` with no authentication, authorization, or callable allowlist check. This makes it possible for unauthenticated attackers to invoke arbitrary loaded PHP functions, enabling a call chain in which the shortcode `$params` array is passed to `edit_user()` — which PHP coerces to integer `1` as the `$user_id` argument — overwriting the credentials of the initial Administrator account (user ID 1) and granting the attacker full wp-admin access. Exploitation is trivially reachable via the plugin's auto-generated `/my-calendar/` page, which is publicly accessible by default upon plugin activation.

References

Source: nvd.nist.gov/vuln/detail/CVE-2026-104798