CVE-2025-39367

Executive Summary

CVE-2025-39367 is a Missing Authorization vulnerability in the SeventhQueen Kleo WordPress theme, affecting versions from n/a through 5.4.3. This flaw allows unauthenticated attackers to access unauthorized functionality or data due to missing capability checks on certain AJAX actions or REST endpoints. The vulnerability has a CVSS score of 5.3 (Medium), with a low EPSS score of 0.0% indicating low exploitation likelihood at this time. No public proof-of-concept or exploit code has been released, and no patch is currently available from the vendor.

Supply Chain & Package Security

This vulnerability affects a WordPress theme distributed via the official WordPress theme repository and commercial marketplaces. Users should verify the integrity of their theme files and monitor for updates from SeventhQueen. Since this is a theme, it is not distributed via NPM, PyPI, Go, or Ruby registries.

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: 5.3 (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) – Impact confined to the vulnerable component.
• Confidentiality Impact: Low (C:L) – Limited information disclosure.
• Integrity Impact: None (I:N) – No data modification.
• Availability Impact: None (A:N) – No denial of service.

Threat Level: Medium. The vulnerability is easy to exploit but only leads to low confidentiality impact. No public exploits exist, but the lack of a patch increases risk over time.

Deep Dive & Mechanics

The vulnerability resides in the Kleo WordPress theme, specifically in its AJAX handler or REST API endpoint that fails to enforce proper authorization checks. WordPress themes often implement custom AJAX actions for front-end functionality (e.g., user profile updates, content loading). If these actions do not verify the user’s capabilities (e.g., wp_verify_nonce() or current_user_can()), an unauthenticated attacker can trigger them.

Root Cause: Missing call to current_user_can() or wp_verify_nonce() in one or more AJAX actions defined in the theme’s functions.php or a dedicated AJAX handler file.

Attack Vector: An attacker sends a crafted HTTP POST/GET request to the WordPress AJAX endpoint (/wp-admin/admin-ajax.php) with a specific action parameter that triggers the vulnerable function. The server processes the request without checking if the user has the required permissions.

Impact: Unauthorized access to sensitive data, such as user lists, private post content, or configuration details. The exact data exposed depends on the vulnerable action.

Vulnerable vs. Patched Code

Since no patch is available, we can only hypothesize the fix. The vulnerable code likely looks like:

// Vulnerable: No capability check
add_action('wp_ajax_nopriv_kleo_get_user_data', 'kleo_get_user_data');
function kleo_get_user_data() {
    $user_id = $_POST['user_id'];
    $user = get_userdata($user_id);
    echo json_encode($user);
    wp_die();
}

The patched version would include:

// Patched: Added capability check
add_action('wp_ajax_nopriv_kleo_get_user_data', 'kleo_get_user_data');
function kleo_get_user_data() {
    if (!current_user_can('edit_users')) {
        wp_die('Unauthorized', 403);
    }
    $user_id = $_POST['user_id'];
    $user = get_userdata($user_id);
    echo json_encode($user);
    wp_die();
}

Exploitation & Lab Setup

Red Team

Prerequisites:

• Target WordPress site running Kleo theme < 5.4.4.
• No authentication required.

Exploitation Steps:

1. Identify the vulnerable AJAX action by analyzing the theme’s JavaScript files (e.g., assets/js/kleo.js) for admin-ajax.php calls.
2. Send a crafted request using curl:

curl -X POST http://target.com/wp-admin/admin-ajax.php \
  -d "action=kleo_get_user_data&user_id=1"

3. If successful, the response will contain sensitive user data (e.g., email, display name).

Note: No public exploit code exists; this is a hypothetical example.

Blue Team

Detection:

• Monitor for unusual AJAX requests to admin-ajax.php with unknown or suspicious action parameters.
• Look for requests from unauthenticated users to actions that should require authentication.

Hunting:

• Search web server logs for POST /wp-admin/admin-ajax.php with action parameters not matching known legitimate actions.
• Use the Sigma rule below to detect unauthorized AJAX access.

Indicators of Compromise (IOCs)

• Network:
  • HTTP POST requests to /wp-admin/admin-ajax.php with action parameters like kleo_get_user_data, kleo_private_content, etc.
  • Response containing JSON with user data (e.g., {"ID":1,"user_email":"admin@example.com"}).
• File:
  • Modified or suspicious entries in the theme’s functions.php or AJAX handler files.
• Log:
  • Web server logs showing 200 responses to unauthenticated AJAX requests that should return 403.

Detection Engineering

YARA Rule

rule Detect_Kleo_Missing_Auth {
    meta:
        description = "Detects Kleo theme files with missing authorization checks"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-39367"
    strings:
        $ajax_action = /add_action\s*\(\s*['\"]wp_ajax_nopriv_[a-z_]+['\"]/
        $no_cap = /current_user_can/
        $no_nonce = /wp_verify_nonce/
    condition:
        $ajax_action and not ($no_cap or $no_nonce)
}

Sigma Rule

title: Unauthorized AJAX Access to Kleo Theme
id: 8f4c3e2a-1b5d-4c7f-9e6a-3d2b1c0f8e7d
status: experimental
description: Detects unauthenticated AJAX requests to Kleo theme actions
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: POST
        cs-uri-stem: '/wp-admin/admin-ajax.php'
        cs-uri-query|contains: 'action=kleo_'
    condition: selection
falsepositives:
    - Legitimate AJAX calls from logged-in users (check for cookies)
level: medium

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-39367 - Unauthorized AJAX Access to Kleo Theme"; flow:to_server,established; http.method; content:"POST"; http.uri; content:"/wp-admin/admin-ajax.php"; http.client_body; content:"action=kleo_"; nocase; classtype:attempted-recon; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the Kleo theme and switch to a default WordPress theme (e.g., Twenty Twenty-Four) until a patch is available.
2. Implement a Web Application Firewall (WAF) rule to block AJAX requests with unknown action parameters.
3. Restrict access to admin-ajax.php using .htaccess or server config:

<Files "admin-ajax.php">
    Require all denied
</Files>

Long-term Fix:

• Monitor the SeventhQueen website for a patched version (5.4.4 or later).
• Apply the patch immediately when released.
• Conduct a code review of all custom AJAX actions to ensure proper authorization.

Workaround:

• Add a custom plugin that hooks into wp_ajax_nopriv_* actions and enforces capability checks.

Valters IT
Securing WordPress Ecosystems