CVE-2025-43838

Executive Summary

CVE-2025-43838 is a Missing Authorization vulnerability (CWE-862) in the Custom PC Builder Lite for WooCommerce WordPress plugin by ChoPlugins.com. This flaw allows an unauthenticated attacker to exploit incorrectly configured access control security levels, potentially leading to unauthorized data access or modification of WooCommerce product configurations. The vulnerability affects all versions up to and including 1.0.1. As of this report, no official patch has been released, and no public proof-of-concept (PoC) code is available. The EPSS score is 0.0%, indicating low exploitation likelihood in the wild, but the risk remains significant for sites using this plugin.

Supply Chain & Package Security

This vulnerability is specific to the WordPress plugin ecosystem. The plugin is distributed via the official WordPress plugin repository and third-party marketplaces. Since no patch is available, site administrators must consider removing or disabling the plugin until a fix is released. The lack of a patch increases supply chain risk, as attackers may target unpatched installations.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
• Base Score: 6.5 (Medium)
• Attack Vector: Network (AV:N) – Exploitable remotely.
• Attack Complexity: Low (AC:L) – No special conditions required.
• Privileges Required: None (PR:N) – No authentication needed.
• User Interaction: None (UI:N) – No user action required.
• Scope: Unchanged (S:U) – Vulnerability does not affect other components.
• Confidentiality Impact: Low (C:L) – Limited data exposure.
• Integrity Impact: Low (I:L) – Limited data modification.
• Availability Impact: None (A:N) – No denial of service.

Threat Level: Medium. While the CVSS score is 6.5, the lack of a patch and the plugin’s popularity in the WooCommerce ecosystem elevate the risk for unmanaged installations.

Deep Dive & Mechanics

The vulnerability resides in the Custom PC Builder Lite for WooCommerce plugin, which allows users to build custom PC configurations on WooCommerce product pages. The plugin fails to properly enforce authorization checks on certain AJAX actions or REST API endpoints, allowing unauthenticated attackers to:

• Access or modify saved PC configurations.
• Retrieve sensitive data such as product pricing, custom options, or user-specific settings.
• Potentially escalate privileges if the plugin interacts with other WordPress roles.

The root cause is the absence of current_user_can() checks or nonce verification in critical functions that handle configuration data. Attackers can craft HTTP requests to these endpoints without a valid session or capability.

Vulnerable vs. Patched Code

Since no patch is available, a comparison cannot be made. However, based on the CWE-862 pattern, the vulnerable code likely resembles:

// Vulnerable: No authorization check
add_action('wp_ajax_nopriv_save_config', 'save_config_callback');
function save_config_callback() {
    // Process and save configuration without checking user capabilities
    $config_data = $_POST['config'];
    update_option('pc_builder_config', $config_data);
    wp_die();
}

A patched version would include:

// Patched: Authorization check added
add_action('wp_ajax_save_config', 'save_config_callback');
add_action('wp_ajax_nopriv_save_config', 'save_config_callback');
function save_config_callback() {
    if (!current_user_can('edit_posts')) {
        wp_die('Unauthorized', 403);
    }
    check_ajax_referer('pc_builder_nonce', 'nonce');
    $config_data = sanitize_text_field($_POST['config']);
    update_option('pc_builder_config', $config_data);
    wp_die();
}

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• Target WordPress site with Custom PC Builder Lite for WooCommerce <= 1.0.1 installed and active.
• No authentication required.

Exploitation Steps:

1. Identify vulnerable endpoints: Use a web proxy or browser developer tools to intercept AJAX requests from the plugin. Look for actions like save_config, load_config, or get_products.

2. Craft a malicious request: Send a POST request to the WordPress admin-ajax.php endpoint with the vulnerable action.

curl -X POST https://target.com/wp-admin/admin-ajax.php \
  -d "action=save_config&config={\"malicious\":\"data\"}"

3. Verify exploitation: Check if the configuration was saved by accessing the plugin’s settings or by sending a GET request to retrieve the data.

curl -X POST https://target.com/wp-admin/admin-ajax.php \
  -d "action=load_config"

Expected Outcome: Unauthorized access to or modification of PC builder configurations.

Blue Team (Detection & Response)

Detection Steps:

1. Monitor AJAX requests: Look for unusual patterns in admin-ajax.php requests, especially those with actions related to the plugin (e.g., save_config, load_config).

2. Check for missing nonces: In WordPress, AJAX actions should include a nonce. Requests without a nonce or with an invalid nonce are suspicious.

3. Review server logs: Search for 403 errors or unexpected POST requests to admin-ajax.php from unauthenticated users.

Response Actions:

• Immediately disable the plugin if exploitation is suspected.
• Review and revert any unauthorized configuration changes.
• Implement a Web Application Firewall (WAF) rule to block requests to vulnerable endpoints without authentication.

Indicators of Compromise (IOCs)

• Network IOCs:

  • POST requests to /wp-admin/admin-ajax.php with parameters action=save_config or action=load_config from unauthenticated IPs.
  • Unusual JSON payloads in the config parameter.

• File IOCs:

  • Modified options in the wp_options table with keys like pc_builder_config.
  • Unexpected entries in the plugin’s custom database tables (if any).

• Log IOCs:

  • Repeated 403 errors from admin-ajax.php with missing nonce.
  • Access logs showing requests to /wp-admin/admin-ajax.php with action=*pc_builder*.

Detection Engineering

YARA Rule

rule Detect_CVE_2025_43838_Exploit {
    meta:
        description = "Detects exploitation attempts for CVE-2025-43838 in Custom PC Builder Lite for WooCommerce"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-43838"
    strings:
        $ajax_action = "action=save_config" nocase
        $ajax_action2 = "action=load_config" nocase
        $plugin_path = "custom-pc-builder-lite-for-woocommerce" nocase
    condition:
        any of ($ajax_action*) and $plugin_path
}

Sigma Rule

title: CVE-2025-43838 - Missing Authorization in Custom PC Builder Lite for WooCommerce
id: 8a4b3c2d-1e5f-4a7b-9c8d-0e1f2a3b4c5d
status: experimental
description: Detects unauthorized AJAX requests to the vulnerable plugin endpoints
author: Valters IT
date: 2025-04-10
references:
    - https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2025-43838
logsource:
    category: webserver
    product: apache
    service: access
detection:
    selection:
        cs-method: 'POST'
        c-uri|contains: '/wp-admin/admin-ajax.php'
        cs-uri-query|contains|all:
            - 'action=save_config'
            - 'action=load_config'
    condition: selection
falsepositives:
    - Legitimate admin actions (if nonce is present)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-43838 - Missing Authorization in Custom PC Builder Lite for WooCommerce"; flow:to_server,established; content:"POST"; http_method; content:"/wp-admin/admin-ajax.php"; http_uri; content:"action=save_config"; http_client_body; nocase; content:"action=load_config"; http_client_body; nocase; reference:cve,2025-43838; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the plugin until a patch is released by the vendor.
2. Remove or rename the plugin directory via FTP or WP-CLI to prevent accidental reactivation.
3. Audit user roles and ensure no unauthorized changes were made to WooCommerce products or configurations.

Long-term Mitigation:

• Monitor the vendor’s website (choplugins.com) for a security update.
• Implement a Web Application Firewall (WAF) with rules to block unauthenticated AJAX requests to the plugin’s endpoints.
• Apply the principle of least privilege to all WordPress plugins and themes.

Workaround (if plugin must remain active):

• Add a custom function to your theme’s functions.php to enforce authorization on the vulnerable endpoints:

add_action('init', function() {
    if (defined('DOING_AJAX') && DOING_AJAX) {
        $action = $_REQUEST['action'] ?? '';
        if (in_array($action, ['save_config', 'load_config'])) {
            if (!current_user_can('edit_posts')) {
                wp_die('Unauthorized', 403);
            }
        }
    }
});

Valters IT
DevSecOps & Cyber Threat Intelligence Division
Report generated on 2025-04-10