CVE-2025-39412

Executive Summary

CVE-2025-39412 is a Missing Authorization vulnerability in the Averta Master Slider WordPress plugin, affecting versions through 3.11.0. This flaw allows unauthenticated attackers to access or modify protected resources due to insufficient access controls on certain plugin functions. The vulnerability has a CVSS score of 4.3 (Medium) and an EPSS score of 0.0%, indicating low exploitation likelihood at this time. As a WordPress plugin vulnerability, it directly impacts the WordPress ecosystem and does not involve Apache or Nginx server software.

Supply Chain & Package Security

This vulnerability affects a WordPress plugin distributed through the official WordPress plugin repository and potentially via third-party marketplaces. The lack of a confirmed patch (UNKNOWN / UNPATCHED) means that users must rely on manual mitigation or removal of the plugin. No OSV or GitHub advisory data is available, and no public exploit code has been released.

CVSS Breakdown & Threat Level

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

The threat level is Medium due to the low complexity and no required privileges, but the impact is limited to low confidentiality loss.

Deep Dive & Mechanics

The vulnerability resides in the Master Slider plugin's REST API or AJAX handlers, where authorization checks are missing. The plugin likely exposes endpoints for creating, editing, or retrieving slider data without verifying user capabilities. An unauthenticated attacker can send crafted HTTP requests to these endpoints to:

• Read sensitive slider configurations (e.g., API keys, custom CSS/JS).
• Modify slider settings (if write endpoints are also unprotected).
• Access non-public slider data intended for authenticated users only.

The core issue is a Missing Authorization (CWE-862) in the plugin's permission validation logic. The plugin fails to call current_user_can() or similar WordPress capability checks before processing requests.

Vulnerable vs. Patched Code

Since no patch is available, the vulnerable code pattern is hypothesized based on common WordPress plugin authorization flaws:

Vulnerable Code (hypothetical):

add_action('wp_ajax_nopriv_masterslider_get_slider', 'masterslider_get_slider');
function masterslider_get_slider() {
    $slider_id = $_GET['slider_id'];
    $slider_data = get_slider_data($slider_id);
    wp_send_json($slider_data);
}

Patched Code (hypothetical):

add_action('wp_ajax_masterslider_get_slider', 'masterslider_get_slider');
add_action('wp_ajax_nopriv_masterslider_get_slider', 'masterslider_get_slider');
function masterslider_get_slider() {
    if (!current_user_can('edit_posts')) {
        wp_die('Unauthorized', 403);
    }
    $slider_id = intval($_GET['slider_id']);
    $slider_data = get_slider_data($slider_id);
    wp_send_json($slider_data);
}

The patch adds a capability check (current_user_can('edit_posts')) and restricts the AJAX action to authenticated users only (removing nopriv or adding proper checks).

Exploitation & Lab Setup

Red Team

Prerequisites:

• Target WordPress site with Master Slider plugin <= 3.11.0.
• Network access to the site.

Exploitation Steps:

1. Identify vulnerable endpoints by analyzing plugin source code or using fuzzing.
2. Send a crafted HTTP request to an unprotected endpoint, e.g.:

   GET /wp-admin/admin-ajax.php?action=masterslider_get_slider&slider_id=1 HTTP/1.1
   Host: target-site.com
   

3. If the endpoint returns slider data without authentication, the vulnerability is confirmed.

Example cURL command:

curl -v "http://target-site.com/wp-admin/admin-ajax.php?action=masterslider_get_slider&slider_id=1"

Blue Team

Detection:

• Monitor for unusual AJAX requests to admin-ajax.php with action parameters containing masterslider_ from unauthenticated sources.
• Look for repeated requests to slider-related endpoints without a valid WordPress nonce.

Hunting:

• Search web server logs for patterns like:

  POST /wp-admin/admin-ajax.php HTTP/1.1" 200
  

  with action=masterslider_ and no Cookie header or invalid nonce.

Lab Setup:

• Install WordPress with Master Slider plugin version 3.11.0.
• Create a test slider with sensitive data.
• Use Burp Suite or OWASP ZAP to intercept and replay requests without authentication.

Indicators of Compromise (IOCs)

• Network IOCs:

  • HTTP requests to /wp-admin/admin-ajax.php with action=masterslider_* parameters from unauthenticated IPs.
  • Unusual GET/POST requests to /wp-json/masterslider/v1/* (if REST API is used).

• File IOCs:

  • Modified slider data in the WordPress database (wp_masterslider table).
  • Unexpected changes to plugin files (though unlikely).

• Log IOCs:

  • Web server logs showing 200 responses to AJAX requests without authentication cookies.

Detection Engineering

YARA Rule

rule detect_master_slider_missing_auth {
    meta:
        description = "Detects exploitation attempts of CVE-2025-39412 in Master Slider plugin"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-39412"
    strings:
        $ajax_action = "masterslider_" nocase
        $admin_ajax = "admin-ajax.php" nocase
        $rest_route = "masterslider/v1" nocase
    condition:
        any of ($ajax_action) and any of ($admin_ajax or $rest_route)
}

Sigma Rule

title: CVE-2025-39412 Master Slider Missing Authorization Exploitation
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects unauthenticated access to Master Slider AJAX endpoints
author: Valters IT
date: 2025-04-10
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2025-39412
logsource:
    category: webserver
    product: apache
    service: access_combined
detection:
    selection:
        cs-uri-query|contains: 
            - 'action=masterslider_'
            - 'masterslider/v1/'
        sc-status: 200
    filter:
        cs(Cookie)|contains: 'wordpress_logged_in_'
    condition: selection and not filter
falsepositives:
    - Legitimate authenticated users (rare)
level: medium
tags:
    - attack.initial_access
    - attack.t1190

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-39412 Master Slider Missing Authorization Exploitation"; flow:to_server; content:"/wp-admin/admin-ajax.php"; http_uri; content:"action=masterslider_"; http_uri; nocase; pcre:"/masterslider_(get|set|update|delete|create)/Ui"; classtype:attempted-recon; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable or remove the Master Slider plugin until a patch is released.
2. Implement a Web Application Firewall (WAF) rule to block requests to admin-ajax.php with action=masterslider_* from unauthenticated users.
3. Restrict access to /wp-admin/admin-ajax.php via .htaccess or server config for non-admin IPs.

Long-term Fix:

• Monitor the Averta plugin repository for an official patch.
• Apply the patch as soon as it becomes available.
• Consider replacing the plugin with an alternative that has active security support.

Workaround Code (if patching is not possible): Add the following to the theme's functions.php to block unauthenticated AJAX requests:

add_action('wp_ajax_nopriv_masterslider_get_slider', function() {
    wp_die('Unauthorized', 403);
}, 1);

Valters IT
DevSecOps & Cyber Threat Intelligence