CVE-2025-52757

Executive Summary

CVE-2025-52757 is a Missing Authorization vulnerability in the SUMO Memberships for WooCommerce WordPress plugin by FantasticPlugins. This flaw allows unauthenticated attackers to exploit incorrectly configured access control security levels, potentially leading to unauthorized access to membership data, privilege escalation, or manipulation of membership statuses. The vulnerability affects all versions prior to 7.8.0. As of this report, no official patch has been released, and the vendor's status is marked as UNKNOWN/UNPATCHED. The CVSS score of 6.5 (Medium) reflects the ease of exploitation (network-based, low complexity, no privileges required) and the potential for limited confidentiality and integrity impact.

WordPress Ecosystem Context

This vulnerability is specific to the WordPress plugin ecosystem. It does not affect Apache, Nginx, or any other web server software. The flaw resides in the plugin's access control logic, which fails to properly validate user permissions for certain AJAX actions or REST API endpoints.

CVSS Breakdown & Threat Level

• Attack Vector (AV): Network (N) – Exploitable remotely.
• Attack Complexity (AC): Low (L) – No special conditions required.
• Privileges Required (PR): None (N) – No authentication needed.
• User Interaction (UI): None (N) – No user action required.
• Scope (S): Unchanged (U) – Exploit does not affect other components.
• Confidentiality (C): Low (L) – Limited data exposure.
• Integrity (I): Low (L) – Limited ability to modify data.
• Availability (A): None (N) – No impact on availability.

Threat Level: Medium. The vulnerability is easy to exploit but has limited impact. However, in a WordPress multisite or membership-based site, the impact could be higher if membership data includes sensitive user information.

Deep Dive & Mechanics

The vulnerability stems from missing authorization checks in the plugin's AJAX handlers or REST API endpoints. In WordPress plugins, it is common to use wp_ajax_ and wp_ajax_nopriv_ hooks to handle authenticated and unauthenticated requests. The SUMO Memberships plugin likely registers actions that should require a user to have a specific capability (e.g., manage_options or edit_posts) but fails to enforce this check.

Root Cause: The plugin does not call current_user_can() or wp_verify_nonce() before processing sensitive actions. This allows any unauthenticated user to trigger functions that modify membership levels, grant access to protected content, or retrieve user data.

Attack Vector: An attacker can send crafted HTTP requests to the WordPress site's AJAX endpoint (/wp-admin/admin-ajax.php) with the appropriate action parameter. For example:

• action=sumomemberships_grant_access
• action=sumomemberships_get_user_data

Without proper capability checks, these actions execute with the privileges of the WordPress core, effectively allowing unauthenticated access.

Vulnerable vs. Patched Code

Vulnerable Code (pre-7.8.0):

add_action('wp_ajax_nopriv_sumomemberships_grant_access', 'sumo_grant_access');
function sumo_grant_access() {
    // No capability check
    $user_id = $_POST['user_id'];
    $membership_id = $_POST['membership_id'];
    // Grant membership logic...
    update_user_meta($user_id, 'sumo_membership', $membership_id);
    wp_die();
}

Patched Code (7.8.0+):

add_action('wp_ajax_nopriv_sumomemberships_grant_access', 'sumo_grant_access');
function sumo_grant_access() {
    // Added capability check
    if (!current_user_can('manage_options')) {
        wp_die('Unauthorized', 403);
    }
    // Verify nonce
    if (!wp_verify_nonce($_POST['_wpnonce'], 'sumo_grant_access_nonce')) {
        wp_die('Nonce verification failed', 403);
    }
    $user_id = intval($_POST['user_id']);
    $membership_id = intval($_POST['membership_id']);
    // Grant membership logic...
    update_user_meta($user_id, 'sumo_membership', $membership_id);
    wp_die();
}

The patched version adds current_user_can('manage_options') and nonce verification, ensuring only authenticated administrators can perform sensitive actions.

Exploitation & Lab Setup

Red Team (Attacker)

Prerequisites:

• A WordPress site running SUMO Memberships < 7.8.0.
• Network access to the site.

Exploitation Steps:

1. Identify the vulnerable AJAX action by analyzing the plugin's source code or using fuzzing.
2. Send a crafted POST request to https://target.com/wp-admin/admin-ajax.php with the following parameters:
   • action=sumomemberships_grant_access
   • user_id=1 (target user ID)
   • membership_id=2 (premium membership ID)
3. The request will execute without authentication, granting the specified user premium membership.

Example cURL command:

curl -X POST https://target.com/wp-admin/admin-ajax.php \
  -d "action=sumomemberships_grant_access&user_id=1&membership_id=2"

Expected Outcome: The user with ID 1 gains premium membership privileges without payment or authorization.

Blue Team (Defender)

Detection Steps:

1. Monitor for unusual AJAX requests to admin-ajax.php with actions related to SUMO Memberships (e.g., sumomemberships_*).
2. Check for requests from unauthenticated users (no Cookie header or invalid nonce).
3. Review server logs for 403 errors after patching (indicates attempted exploitation).

Honeypot Setup:

• Create a fake AJAX endpoint that logs all requests and alerts on suspicious patterns.
• Use a Web Application Firewall (WAF) rule to block requests to admin-ajax.php with action parameters containing sumomemberships unless the request includes a valid nonce.

Indicators of Compromise (IOCs)

• Network IOCs:

  • POST requests to /wp-admin/admin-ajax.php with action=sumomemberships_* parameters.
  • Absence of Cookie header in such requests.
  • Repeated requests with different user_id values.

• File IOCs:

  • Modified user meta entries: sumo_membership for unauthorized users.
  • Plugin files not updated to version 7.8.0 or later.

• Log IOCs:

  • Apache/Nginx access logs showing POST /wp-admin/admin-ajax.php HTTP/1.1 with 200 responses for unauthenticated users.
  • PHP error logs showing warnings about undefined capabilities.

Detection Engineering

YARA Rule

rule CVE_2025_52757_SUMO_Memberships_Missing_Auth {
    meta:
        description = "Detects missing authorization in SUMO Memberships for WooCommerce plugin"
        author = "Valters IT"
        date = "2025-04-10"
        cve = "CVE-2025-52757"
    strings:
        $vuln_action = "sumomemberships_grant_access" nocase
        $vuln_action2 = "sumomemberships_get_user_data" nocase
        $no_cap_check = "current_user_can" nocase
    condition:
        ($vuln_action or $vuln_action2) and not $no_cap_check
}

Sigma Rule

title: CVE-2025-52757 - SUMO Memberships Missing Authorization
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects exploitation attempts of missing authorization in SUMO Memberships plugin
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: POST
        cs-uri-query: 
            - "*action=sumomemberships_*"
        sc-status: 200
    condition: selection
falsepositives:
    - Legitimate admin actions (requires authentication)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-52757 - SUMO Memberships Missing Authorization Exploit"; flow:to_server,established; content:"POST"; http_method; content:"/wp-admin/admin-ajax.php"; http_uri; content:"action=sumomemberships_"; http_client_body; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Update the plugin to version 7.8.0 or later if available. If not, disable the plugin until a patch is released.
2. Implement a Web Application Firewall (WAF) rule to block unauthenticated requests to admin-ajax.php with action parameters containing sumomemberships.
3. Monitor logs for suspicious AJAX requests and investigate any unauthorized membership changes.

Long-term Measures:

1. Apply the principle of least privilege to all WordPress plugins. Regularly audit plugin code for missing authorization checks.
2. Use a security plugin like Wordfence or Sucuri to add an extra layer of protection.
3. Enable nonce verification for all AJAX actions in custom plugins.
4. Conduct regular vulnerability scans using tools like WPScan.

Workaround (if patch is unavailable):

• Add a custom function to your theme's functions.php to block unauthenticated access to vulnerable actions:

add_action('init', function() {
    if (defined('DOING_AJAX') && DOING_AJAX) {
        $action = $_REQUEST['action'] ?? '';
        if (strpos($action, 'sumomemberships_') === 0 && !is_user_logged_in()) {
            wp_die('Unauthorized', 403);
        }
    }
});

Valters IT
Securing Digital Frontiers