CVE-2025-49376

Executive Summary

CVE-2025-49376 is a Missing Authorization vulnerability in the DELUCKS SEO WordPress plugin, affecting versions up to and including 2.5.9. This flaw allows unauthenticated attackers to access functionality that should be constrained by Access Control Lists (ACLs). The vulnerability has a CVSS score of 5.3 (Medium), with a low EPSS score of 0.0% indicating low exploitation activity at the time of analysis. No public proof-of-concept (PoC) code or patch is currently available.

Supply Chain & Package Security

This vulnerability resides in a WordPress plugin ecosystem. The plugin is distributed via the official WordPress plugin repository and potentially third-party marketplaces. Users are advised to verify the integrity of their plugin files and monitor for updates from the vendor. Since no patch is available, the supply chain risk is elevated for any site running the affected version.

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 remotely without authentication, but the impact is limited to low confidentiality loss. The lack of a patch increases the risk for unpatched installations.

Deep Dive & Mechanics

The vulnerability stems from missing authorization checks in the DELUCKS SEO plugin’s AJAX handlers or REST API endpoints. The plugin likely exposes administrative or privileged functions (e.g., fetching SEO data, modifying settings, or accessing internal logs) without verifying the user’s capabilities. An unauthenticated attacker can directly call these endpoints, bypassing WordPress’s capability checks.

Root Cause: The plugin fails to implement current_user_can() or similar capability checks before executing sensitive operations. This allows any visitor to trigger actions intended only for administrators or editors.

Attack Vector: An attacker sends crafted HTTP requests to the vulnerable endpoints, such as:

POST /wp-admin/admin-ajax.php?action=delucks_seo_fetch_data

or

GET /wp-json/delucks-seo/v1/settings

The server processes the request without verifying the user’s role, leading to unauthorized access.

Vulnerable vs. Patched Code

Since no patch is available, the vulnerable code pattern is described below. A patched version would include proper authorization checks.

Vulnerable Code (PHP):

add_action('wp_ajax_nopriv_delucks_seo_fetch_data', 'delucks_seo_fetch_data');
function delucks_seo_fetch_data() {
    // No capability check
    $data = get_option('delucks_seo_settings');
    wp_send_json_success($data);
}

Patched Code (Hypothetical):

add_action('wp_ajax_nopriv_delucks_seo_fetch_data', 'delucks_seo_fetch_data');
function delucks_seo_fetch_data() {
    if (!current_user_can('manage_options')) {
        wp_die('Unauthorized', 403);
    }
    $data = get_option('delucks_seo_settings');
    wp_send_json_success($data);
}

Exploitation & Lab Setup

Red Team

Prerequisites:

• A WordPress site with DELUCKS SEO plugin version <= 2.5.9 installed and activated.
• Network access to the target.

Exploitation Steps:

1. Identify vulnerable endpoints by analyzing the plugin’s JavaScript or source code for AJAX actions.
2. Send an unauthenticated request to trigger the missing authorization:

   curl -X POST http://target/wp-admin/admin-ajax.php \
        -d "action=delucks_seo_fetch_data"
   

3. If successful, the response will contain sensitive data (e.g., SEO settings, API keys, or internal logs).

Example Request:

POST /wp-admin/admin-ajax.php HTTP/1.1
Host: target.com
Content-Type: application/x-www-form-urlencoded
Content-Length: 30

action=delucks_seo_fetch_data

Blue Team

Detection & Response:

• Monitor for unusual AJAX requests to admin-ajax.php with actions prefixed by delucks_seo_ from unauthenticated users.
• Check web server logs for 403 errors on plugin-specific endpoints (if patched) or successful responses to unauthorized requests.
• Use the detection rules below to identify exploitation attempts.

Indicators of Compromise (IOCs)

• Network IOCs:
  • HTTP requests to /wp-admin/admin-ajax.php with action=delucks_seo_* parameters from unauthenticated sources.
  • Requests to /wp-json/delucks-seo/v1/* endpoints without valid authentication tokens.
• File IOCs:
  • Modified plugin files in /wp-content/plugins/delucks-seo/ (e.g., added backdoors).
  • Unexpected files in the uploads directory.
• Log IOCs:
  • Repeated 200 responses to admin-ajax.php from IPs not associated with admin users.
  • PHP error logs showing Undefined index or capability-related warnings.

Detection Engineering

YARA Rule

rule CVE_2025_49376_DELUCKS_SEO_Missing_Auth {
    meta:
        description = "Detects missing authorization in DELUCKS SEO plugin"
        author = "Valters IT"
        date = "2025-04-10"
        cve = "CVE-2025-49376"
    strings:
        $ajax_action = "delucks_seo_" nocase
        $nopriv = "wp_ajax_nopriv_" nocase
        $missing_cap = /current_user_can\s*\(/ nocase
    condition:
        $ajax_action and $nopriv and not $missing_cap
}

Sigma Rule

title: CVE-2025-49376 - DELUCKS SEO Missing Authorization
id: 12345678-1234-1234-1234-123456789abc
status: experimental
description: Detects unauthenticated access to DELUCKS SEO plugin AJAX endpoints
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
    service: access
detection:
    selection:
        cs-method: 'POST'
        cs-uri-query|contains: 'action=delucks_seo_'
        sc-status: 200
    condition: selection
falsepositives:
    - Legitimate admin users (if authentication is properly implemented)
level: medium

Suricata Rule

alert http any any -> any any (
    msg:"CVE-2025-49376 - DELUCKS SEO Missing Authorization Attempt";
    flow:to_server,established;
    content:"POST"; http_method;
    content:"admin-ajax.php"; http_uri;
    content:"action=delucks_seo_"; http_client_body;
    classtype:attempted-recon;
    sid:1000001;
    rev:1;
)

Remediation & Mitigation

Immediate Actions:

1. Disable the plugin if not essential, until a patch is released.
2. Implement a Web Application Firewall (WAF) rule to block requests to admin-ajax.php with action=delucks_seo_* from unauthenticated users.
3. Restrict access to /wp-admin/ via IP whitelisting or VPN.

Long-Term Fix:

• Apply the vendor patch as soon as it becomes available.
• Conduct a code review of the plugin to ensure all AJAX and REST endpoints implement proper capability checks using current_user_can() or check_admin_referer().

Workaround (if plugin must remain active):

• Add the following code to the theme’s functions.php to block unauthenticated access:

add_action('init', function() {
    if (defined('DOING_AJAX') && DOING_AJAX && !is_user_logged_in()) {
        $action = $_REQUEST['action'] ?? '';
        if (strpos($action, 'delucks_seo_') === 0) {
            wp_die('Unauthorized', 403);
        }
    }
});

Valters IT
Securing WordPress, One Plugin at a Time