CVE-2026-28038: Ultimate Addons for WPBakery Bypass Flaw

CVE-2026-28038 Overview

CVE-2026-28038 is a Missing Authorization vulnerability affecting the Ultimate Addons for WPBakery Page Builder plugin developed by Brainstorm Force. This WordPress plugin vulnerability allows attackers to exploit incorrectly configured access control security levels, potentially leading to unauthorized modifications of website content and settings.

The vulnerability stems from broken access control mechanisms within the ultimate_vc_addons plugin, enabling authenticated users with low-level privileges to perform actions that should be restricted to administrators or other higher-privileged roles.

Critical Impact

Authenticated attackers can bypass authorization checks to modify protected resources, potentially compromising site integrity without proper administrative privileges.

Affected Products

• Ultimate Addons for WPBakery Page Builder versions up to and including 3.21.1
• WordPress installations using the ultimate_vc_addons plugin
• WPBakery Page Builder deployments with Ultimate Addons extension enabled

Discovery Timeline

• 2026-03-05 - CVE-2026-28038 published to NVD
• 2026-03-05 - Last updated in NVD database

Technical Details for CVE-2026-28038

Vulnerability Analysis

This vulnerability is classified under CWE-862 (Missing Authorization), indicating that the affected plugin fails to perform proper authorization checks before allowing users to execute sensitive operations. The missing authorization allows low-privileged authenticated users to bypass intended access restrictions and manipulate plugin functionality or associated data.

The attack requires network access and authentication with minimal privileges. Once authenticated, an attacker can exploit the misconfigured access controls to achieve high-integrity impact on the target system, potentially modifying content, settings, or other protected elements without appropriate authorization.

Root Cause

The root cause of CVE-2026-28038 lies in the plugin's failure to implement proper capability checks on sensitive AJAX endpoints or administrative functions. The ultimate_vc_addons plugin does not adequately verify that the currently authenticated user possesses the required permissions before processing certain requests. This oversight allows subscribers, contributors, or other low-privileged WordPress users to access functionality intended only for administrators.

Attack Vector

The attack vector is network-based and requires an authenticated session with low-level privileges on the target WordPress installation. An attacker would:

1. Create or compromise a low-privileged account (e.g., subscriber or contributor role)
2. Authenticate to the WordPress site
3. Send crafted requests to vulnerable endpoints within the Ultimate Addons plugin
4. Bypass authorization checks due to missing capability validation
5. Perform unauthorized modifications to plugin settings or site content

The vulnerability requires no user interaction and has low attack complexity, making it relatively straightforward for an authenticated attacker to exploit. While confidentiality is not impacted, the integrity impact is high, meaning attackers can significantly alter protected data or configurations.

Detection Methods for CVE-2026-28038

Indicators of Compromise

• Unexpected modifications to WPBakery page builder elements or layouts by non-administrative users
• Suspicious AJAX requests to Ultimate Addons endpoints from low-privileged user accounts
• Audit log entries showing plugin setting changes by unauthorized user roles
• Anomalous POST requests targeting ultimate_vc_addons related endpoints

Detection Strategies

• Implement WordPress security logging to track all plugin-related administrative actions and the user roles performing them
• Monitor AJAX request patterns for unusual access to Ultimate Addons endpoints by non-admin users
• Deploy web application firewall (WAF) rules to detect and block unauthorized access attempts to plugin administrative functions
• Utilize file integrity monitoring to detect unexpected changes to plugin configurations or associated database entries

Monitoring Recommendations

• Enable comprehensive audit logging for all WordPress user actions, particularly those affecting plugin configurations
• Configure alerts for any plugin setting modifications performed by users without administrator capabilities
• Regularly review access logs for patterns indicating privilege abuse or unauthorized endpoint access
• Implement real-time monitoring for critical WordPress admin AJAX endpoints

How to Mitigate CVE-2026-28038

Immediate Actions Required

• Update Ultimate Addons for WPBakery Page Builder to a patched version newer than 3.21.1 when available
• Review and audit all user accounts on affected WordPress installations, removing unnecessary low-privileged accounts
• Implement additional access controls at the web server or WAF level to restrict access to vulnerable endpoints
• Temporarily disable the Ultimate Addons plugin if a patch is not yet available and the functionality is non-critical

Patch Information

Users should monitor the official Brainstorm Force channels and the WordPress plugin repository for security updates addressing this vulnerability. The Patchstack vulnerability database provides additional details and tracking for this issue.

Organizations should subscribe to security advisories from both Brainstorm Force and their preferred WordPress security intelligence sources to receive timely notifications when patches become available.

Workarounds

• Restrict user registration on the WordPress site to prevent unauthorized account creation
• Implement additional authentication layers (such as two-factor authentication) for all user accounts
• Use a WordPress security plugin to add capability-based restrictions on sensitive plugin endpoints
• Consider network-level access controls to limit access to the WordPress admin area to trusted IP addresses

# Configuration example - Restrict access to WordPress admin via .htaccess
# Add to .htaccess in wp-admin directory
<Files "admin-ajax.php">
    # Allow authenticated requests but log suspicious patterns
    SetEnvIf Request_URI "ultimate_vc" potential_vuln_access
    CustomLog /var/log/apache2/ultimate_addons_access.log combined env=potential_vuln_access
</Files>

# Alternatively, restrict admin access by IP
<IfModule mod_authz_core.c>
    Require ip 192.168.1.0/24
    Require ip 10.0.0.0/8
</IfModule>