CVE-2026-104798

9.8 CRITICAL 0.5% exploit odds No fix listed Auth & access Web app

What it is

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.

At a glance

Exploitability: Can be exploited over the network without logging in. High risk of data exposure, data tampering, service disruption.
Exploit odds: 0.5% chance of exploitation in the next 30 days (EPSS).
Fix: No patch or advisory is linked yet. Look at mitigations or restrict exposure.

Timeline

2026-10-02 13:12 UTC ReservedThe CVE id was reserved by its CNA
2026-10-16 05:17 UTC PublishedDisclosed publicly on CVE.org and NVD
2026-10-16 18:17 UTC Last updatedMost recent change to the record

Why it ranks here

Exploited in the wild: no, CISA does not list it.
Exploit odds: 0.5% in the next 30 days (EPSS).
Severity: 9.8 CRITICAL (CVSS).
Fix: none linked yet, which raises it.

Details

Published: 2026-10-16 05:17 UTC
Last modified: 2026-10-16 18:17 UTC
Exploit probability: 0.5% · EPSS, next 30 days
Weakness: CWE-269 · Improper privilege management
Record status: Deferred

Attack profile CVSS 3.1 · 9.8

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

Raw vector

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

Is it in your code?

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Read https://cve-list.com/agent/cve/CVE-2026-104798.md and follow it. Check whether this project is affected by CVE-2026-104798. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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References

NVD record · CVE.org record