CVE-2025-39353

Executive Summary

CVE-2025-39353 identifies a Missing Authorization vulnerability in the Themegoods Grand Restaurant WordPress theme, affecting versions up to and including 7.0. This flaw allows an unauthenticated attacker to exploit incorrectly configured access control security levels, potentially leading to unauthorized access to sensitive data or functionality. The vulnerability is classified as a WordPress ecosystem issue, residing entirely within the theme’s codebase and not attributable to the underlying web server (Apache/Nginx). With a CVSS score of 5.3 (Medium), the risk is elevated due to the low attack complexity and no required privileges. No public proof-of-concept (PoC) or exploit code is currently available, but the lack of a patch from the vendor increases the urgency for defensive measures.

Supply Chain & Package Security

This vulnerability affects a commercial WordPress theme distributed via ThemeForest and other marketplaces. As a WordPress plugin/theme, it is part of a supply chain where end-users rely on the vendor (Themegoods) for updates. The absence of a patch means that all installations of Grand Restaurant <= 7.0 are at risk. Organizations should treat this as a supply chain risk, verifying the integrity of the theme files and monitoring for vendor updates.

CVSS Breakdown & Threat Level

• CVSS Score: 5.3 (Medium)
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
• Attack Vector (AV): Network – The vulnerability can be exploited remotely.
• Attack Complexity (AC): Low – No special conditions are required.
• Privileges Required (PR): None – No authentication needed.
• User Interaction (UI): None – No user action is required.
• Scope (S): Unchanged – The exploit cannot affect other components.
• Confidentiality (C): Low – Limited information disclosure is possible.
• Integrity (I): None – No data modification is possible.
• Availability (A): None – No denial-of-service impact.

Threat Level: Medium. The low EPSS score (0.0%) suggests limited active exploitation, but the lack of a patch and the ease of exploitation (no privileges, low complexity) make it a potential target for automated scanning.

Deep Dive & Mechanics

The vulnerability stems from a Missing Authorization check (CWE-862) in the Grand Restaurant theme. In WordPress themes, certain AJAX actions, REST API endpoints, or template files may be exposed without verifying that the requesting user has the necessary capabilities (e.g., edit_posts, manage_options). An unauthenticated attacker can directly call these endpoints to access or modify data that should be restricted.

Root Cause: The theme likely registers WordPress AJAX actions or REST routes without implementing current_user_can() checks or nonce verification. For example, a function like grandrestaurant_get_private_data() might be hooked to wp_ajax_nopriv_* (allowing unauthenticated access) or wp_ajax_* without proper capability checks.

Attack Vector: An attacker sends crafted HTTP requests to the WordPress site, targeting the vulnerable endpoint. Since no authentication is required, the attack can be performed by anyone with network access to the site.

Impact: Successful exploitation could lead to:

• Unauthorized access to private theme settings, customer data, or reservation details.
• Disclosure of sensitive configuration information (e.g., API keys, database credentials if stored in theme options).
• Potential privilege escalation if the endpoint allows modification of user roles or options.

Vulnerable vs. Patched Code

Since no patch is available, the following is a hypothetical example of the vulnerable code pattern and how it should be fixed.

Vulnerable Code (functions.php or similar):

add_action('wp_ajax_nopriv_grandrestaurant_get_data', 'grandrestaurant_get_data');
function grandrestaurant_get_data() {
    // No capability check
    $data = get_option('grandrestaurant_private_data');
    wp_send_json_success($data);
}

Patched Code (hypothetical fix):

add_action('wp_ajax_grandrestaurant_get_data', 'grandrestaurant_get_data');
add_action('wp_ajax_nopriv_grandrestaurant_get_data', 'grandrestaurant_get_data_noauth');
function grandrestaurant_get_data() {
    if (!current_user_can('manage_options')) {
        wp_die('Unauthorized', 403);
    }
    $data = get_option('grandrestaurant_private_data');
    wp_send_json_success($data);
}
function grandrestaurant_get_data_noauth() {
    wp_die('Unauthorized', 403);
}

The patched version restricts the AJAX action to authenticated users with the manage_options capability and explicitly denies unauthenticated access.

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• A WordPress site running Grand Restaurant theme <= 7.0.
• Network access to the target.

Steps:

1. Identify Vulnerable Endpoints: Use a tool like Burp Suite or WPScan to enumerate AJAX actions. Look for actions prefixed with grandrestaurant_ that are registered with wp_ajax_nopriv_*.
2. Craft Exploit Request: Send a POST request to the WordPress admin-ajax.php endpoint with the action parameter.

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

3. Analyze Response: If the response contains sensitive data (e.g., JSON with private options), the exploit is successful.

Note: No public exploit code is available, so this is a generic approach.

Blue Team (Detection & Hardening)

Detection:

• Monitor for unusual requests to /wp-admin/admin-ajax.php with unknown or suspicious action parameters.
• Look for requests from unauthenticated users that return non-standard data (e.g., JSON with configuration details).

Hardening:

• Immediate: Disable the Grand Restaurant theme until a patch is available. Switch to a different theme.
• Workaround: If the theme must be used, implement a custom plugin that adds capability checks to all AJAX actions. For example:

  add_action('init', function() {
      if (defined('DOING_AJAX') && DOING_AJAX) {
          // Block all nopriv actions for grandrestaurant
          add_action('wp_ajax_nopriv_grandrestaurant_get_data', function() {
              wp_die('Unauthorized', 403);
          }, 1);
      }
  });
  

• Web Application Firewall (WAF): Create rules to block requests to admin-ajax.php with action parameters matching grandrestaurant_* from unauthenticated users.

Indicators of Compromise (IOCs)

• Network IOCs:
  • HTTP POST requests to /wp-admin/admin-ajax.php with action=grandrestaurant_* parameters.
  • Responses containing JSON data with keys like success:true and unexpected data fields.
• File IOCs:
  • Presence of the Grand Restaurant theme in /wp-content/themes/grandrestaurant/ with version <= 7.0.
• Log IOCs:
  • Web server logs showing repeated 200 responses to admin-ajax.php from IPs with no prior authentication.

Detection Engineering

YARA Rule

rule Detect_GrandRestaurant_Vulnerable_Theme {
    meta:
        description = "Detects vulnerable Grand Restaurant theme files (<= 7.0)"
        author = "Valters IT"
        date = "2025-04-10"
        cve = "CVE-2025-39353"
    strings:
        $theme_name = "Grand Restaurant"
        $version_string = "Version: 7.0" nocase
        $vuln_pattern = "wp_ajax_nopriv_grandrestaurant" nocase
    condition:
        $theme_name and ($version_string or $vuln_pattern)
}

Sigma Rule

title: Unauthenticated AJAX Request to Grand Restaurant Endpoint
id: 8a9b3c4d-5e6f-7a8b-9c0d-1e2f3a4b5c6d
status: experimental
description: Detects unauthenticated POST requests to admin-ajax.php with grandrestaurant action parameters.
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
    service: access
detection:
    selection:
        cs-method: POST
        cs-uri-query|contains: admin-ajax.php
        cs-uri-query|contains: action=grandrestaurant_
    condition: selection
falsepositives:
    - Legitimate theme functionality if misconfigured
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-39353 Grand Restaurant Unauthenticated AJAX Access"; flow:to_server,established; content:"POST"; http_method; content:"/wp-admin/admin-ajax.php"; http_uri; content:"action=grandrestaurant_"; http_client_body; classtype:attempted-recon; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the Grand Restaurant theme and switch to a secure alternative.
2. Apply a virtual patch using a WAF to block unauthenticated requests to admin-ajax.php with grandrestaurant_* actions.
3. Monitor logs for exploitation attempts and block offending IPs.

Long-Term Fix:

• Vendor Patch: Await an official update from Themegoods. Contact the vendor for an ETA.
• Custom Fix: If you have development resources, manually add capability checks to all AJAX actions in the theme (see Vulnerable vs. Patched Code section).
• Replace Theme: Consider migrating to a different, actively maintained WordPress restaurant theme.

Valters IT Signature: This report is provided as-is for educational and defensive purposes. Always validate findings in a controlled environment before applying changes.