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CVE-2026-104798 — The My Calendar – Accessible Event Manager plugin for WordPress is vulnerable to…

Key facts

CVE-2026-104798 is a Critical (9.8) vulnerability: The My Calendar – Accessible Event Manager plugin for WordPress is vulnerable to…. This entry ships a detection-only PoC and a Docker test lab.
CVE CVE-2026-104798
Severity Critical (9.8)
Detection / prevention —
PoC poc.py
Source 2026/CVE-2026-104798/

Details

English | 한국어

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.

Vulnerability Details

Property Value
CVE ID CVE-2026-104798
Type RCE
CVSS Score 9.8

Proof of Concept

Download

# Download PoC script
curl -O https://raw.githubusercontent.com/fankh/vulnerability-poc/main/2026/CVE-2026-104798/poc.py

Usage

# Run PoC against target
python3 poc.py --target <TARGET_URL>

# With authentication
python3 poc.py --target <TARGET_URL> --username <USER> --password <PASS>

⚠️ Warning: This PoC is for authorized security testing only. It uses detection-only techniques and does not exploit or damage target systems.

Test Lab

This repository includes a Docker-based test environment with both vulnerable and patched applications.

Quick Start

# Clone and navigate to CVE directory
cd CVE-2026-104798

# Start both applications
docker-compose up -d

# Run tests
./run-tests.sh    # Linux/Mac
./run-tests.ps1   # Windows PowerShell

Application Endpoints

Application URL Status
Vulnerable App http://localhost:8080 Shows vulnerability
Patched App http://localhost:8081 Demonstrates fix

Directory Structure

├── README.md           # English documentation
├── README_KO.md        # Korean documentation
├── poc.py              # PoC detection script
├── docker-compose.yml  # Container orchestration
├── run-tests.sh        # Linux/Mac test runner
├── run-tests.ps1       # Windows test runner
├── vulnerable-app/     # Vulnerable version
│   ├── app.py
│   ├── Dockerfile
│   └── requirements.txt
└── patched-app/        # Fixed version
    ├── app.py
    ├── Dockerfile
    └── requirements.txt

References

  • https://plugins.trac.wordpress.org/browser/my-calendar/tags/3.8.6/my-calendar-navigation.php#L248
  • https://plugins.trac.wordpress.org/browser/my-calendar/tags/3.8.6/my-calendar-navigation.php#L260
  • https://plugins.trac.wordpress.org/browser/my-calendar/tags/3.8.6/my-calendar-output.php#L1622
  • https://plugins.trac.wordpress.org/browser/my-calendar/tags/3.8.6/my-calendar-search.php#L170
  • https://plugins.trac.wordpress.org/browser/my-calendar/tags/3.8.6/my-calendar-search.php#L221
  • https://plugins.trac.wordpress.org/browser/my-calendar/tags/3.8.6/my-calendar-shortcodes.php#L102
  • https://plugins.trac.wordpress.org/changeset?reponame=&old=3746389%40my-calendar&new=3746389%40my-calendar
  • https://www.wordfence.com/threat-intel/vulnerabilities/id/e8aa6ee7-525e-4458-9f5b-1e729afe448c?source=cve

Generated by PoC Generator on 2026-10-16T22:09:58.445486231

Frequently asked questions

What is CVE-2026-104798?

CVE-2026-104798 is a Critical (9.8) vulnerability: The My Calendar – Accessible Event Manager plugin for WordPress is vulnerable to…. This entry ships a detection-only PoC and a Docker test lab.

How do I detect CVE-2026-104798?

Run the detection-only PoC included with this entry against your Docker test lab to confirm whether a target is affected; pair it with your own IDS logging.

How do I block or mitigate CVE-2026-104798?

Upgrade to a fixed version per the vendor advisory; the NVD record lists the affected versions. Use the included PoC to verify your remediation.

For authorized security testing and research only. See the full source and NVD record.