CVE-2025-12526

Executive Summary

CVE-2025-12526 is a Missing Authorization vulnerability in the Private Google Calendars WordPress plugin, affecting all versions up to and including 20250811. The flaw resides in the pgc_remove AJAX action, which lacks a proper capability check. This allows authenticated attackers with Subscriber-level access or higher to reset the plugin’s settings without authorization. The vulnerability has a CVSS score of 4.3 (Medium) and an EPSS score of 0.0%, indicating low exploitation likelihood at this time. No public exploit code or patch is currently available.

Supply Chain & Package Security

This vulnerability is specific to the WordPress plugin ecosystem. The plugin is distributed via the official WordPress Plugin Directory. Users are advised to monitor the plugin’s page for updates and verify the integrity of the plugin files using checksums provided by WordPress.org.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N
• Base Score: 4.3 (Medium)
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: Low (Subscriber)
• User Interaction: None
• Scope: Unchanged
• Confidentiality Impact: None
• Integrity Impact: Low (Settings reset)
• Availability Impact: None

Threat Level: Medium. While the impact is limited to settings reset, it can disrupt calendar functionality and potentially expose misconfigurations.

Deep Dive & Mechanics

The vulnerability is a classic Missing Authorization (CWE-862) issue. The plugin registers an AJAX action pgc_remove intended for administrators to reset plugin settings. However, the callback function does not perform a current_user_can() check or any capability verification. As a result, any authenticated user, including Subscribers, can trigger the action.

Root Cause: The pgc_remove function in the plugin’s main PHP file (likely private-google-calendars.php) directly executes delete_option() or similar reset logic without verifying user permissions.

Attack Flow:

1. Attacker authenticates as a Subscriber (or higher).
2. Attacker sends a POST request to /wp-admin/admin-ajax.php with action=pgc_remove.
3. The plugin resets its settings to defaults, potentially breaking calendar integrations.

Vulnerable vs. Patched Code

Vulnerable Code (<= 20250811):

add_action('wp_ajax_pgc_remove', 'pgc_remove_callback');
function pgc_remove_callback() {
    // No capability check
    delete_option('pgc_settings');
    wp_die();
}

Patched Code (Hypothetical):

add_action('wp_ajax_pgc_remove', 'pgc_remove_callback');
function pgc_remove_callback() {
    if (!current_user_can('manage_options')) {
        wp_die('Unauthorized', 403);
    }
    delete_option('pgc_settings');
    wp_die();
}

Exploitation & Lab Setup

Red Team

Prerequisites: Valid WordPress user account with Subscriber role or higher.

Exploitation Steps:

1. Log in to WordPress as a Subscriber.
2. Send a crafted POST request using cURL:

curl -X POST 'http://target.com/wp-admin/admin-ajax.php' \
  -d 'action=pgc_remove' \
  --cookie 'wordpress_logged_in_<hash>=<session_cookie>'

3. Verify the plugin settings are reset (e.g., calendar feeds break).

Note: No public exploit code is available; this is a manual exploitation scenario.

Blue Team

Detection & Response:

• Monitor AJAX requests to admin-ajax.php with action=pgc_remove from non-admin users.
• Alert on sudden plugin setting changes or calendar feed failures.
• Review user role assignments; restrict Subscriber accounts.

Indicators of Compromise (IOCs)

• Network: POST requests to /wp-admin/admin-ajax.php with body action=pgc_remove.
• Logs: WordPress debug log entries showing pgc_remove action triggered by low-privilege users.
• System: Plugin settings (pgc_settings option) unexpectedly reset to defaults.

Detection Engineering

YARA Rule

rule Detect_PGC_Remove_Exploit {
    meta:
        description = "Detects exploitation attempts of CVE-2025-12526 in Private Google Calendars plugin"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-12526"
    strings:
        $ajax_action = "action=pgc_remove"
        $wp_ajax = "admin-ajax.php"
    condition:
        $ajax_action and $wp_ajax
}

Sigma Rule

title: CVE-2025-12526 - Private Google Calendars Settings Reset
id: 8a3f7c2e-9b1d-4f5a-8c6d-2e3f4a5b6c7d
status: experimental
description: Detects unauthorized pgc_remove AJAX action from low-privilege users
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: POST
        cs-uri-query|contains: 'admin-ajax.php'
        cs-uri-query|contains: 'action=pgc_remove'
    condition: selection
falsepositives:
    - Legitimate admin actions (rare)
level: medium

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"CVE-2025-12526 - Private Google Calendars Settings Reset Attempt";
    flow:to_server,established;
    content:"POST"; http_method;
    content:"admin-ajax.php"; http_uri;
    content:"action=pgc_remove"; http_client_body;
    classtype:attempted-recon;
    sid:1000001;
    rev:1;
)

Remediation & Mitigation

Immediate Actions:

1. Disable the plugin until a patch is released.
2. Restrict user roles – ensure Subscriber accounts are not granted unnecessary access.
3. Implement a Web Application Firewall (WAF) rule to block pgc_remove AJAX requests from non-admin users.

Long-term Fix:

• Apply a capability check (current_user_can('manage_options')) in the pgc_remove callback.
• Monitor the plugin’s official page for updates.

Workaround:

• Add custom code to a site-specific plugin or theme’s functions.php:

add_action('init', function() {
    if (defined('DOING_AJAX') && DOING_AJAX && isset($_POST['action']) && $_POST['action'] === 'pgc_remove') {
        if (!current_user_can('manage_options')) {
            wp_die('Unauthorized', 403);
        }
    }
});

Valters IT
Securing Digital Frontiers