CVE-2024-53805

Executive Summary

CVE-2024-53805 is a Missing Authorization vulnerability in the WP Mailster WordPress plugin, affecting versions up to and including 1.8.16.0. This flaw allows unauthenticated attackers to exploit incorrectly configured access control security levels, potentially leading to unauthorized data access or privilege escalation. The vulnerability has a CVSS score of 7.5 (High), with a vector indicating network-based exploitation with low complexity and no privileges required. No public proof-of-concept (PoC) or exploit code has been identified at this time, and the patch status remains unknown.

Supply Chain & Package Security

This vulnerability affects a WordPress plugin distributed via the official WordPress plugin repository. Users are advised to monitor for updates from the vendor and apply patches as soon as they become available. The plugin is not distributed via NPM, PyPI, Go, or Ruby ecosystems.

CVSS Breakdown & Threat Level

• CVSS Score: 7.5 (High)
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
• Attack Vector: Network (AV:N)
• Attack Complexity: Low (AC:L)
• Privileges Required: None (PR:N)
• User Interaction: None (UI:N)
• Scope: Unchanged (S:U)
• Confidentiality Impact: High (C:H)
• Integrity Impact: None (I:N)
• Availability Impact: None (A:N)

The vulnerability is classified as High severity due to the potential for unauthorized data exposure without any authentication or user interaction.

Deep Dive & Mechanics

The vulnerability resides in the WP Mailster plugin, which is used for email marketing and newsletter management within WordPress. The issue stems from Missing Authorization (CWE-862) in one or more plugin endpoints or functions. This means that the plugin fails to properly verify that a user has the necessary permissions before performing sensitive actions or accessing protected data.

Attackers can exploit this by sending crafted HTTP requests to vulnerable endpoints, bypassing access controls. The exact affected functionality is not publicly detailed, but given the plugin's purpose, it likely involves accessing subscriber lists, email templates, or configuration settings. The lack of authentication checks allows unauthenticated attackers to retrieve sensitive information, such as email addresses or API keys.

Vulnerable vs. Patched Code

Since no official patch has been released, a direct code comparison is not possible. However, the vulnerability likely exists in functions that handle AJAX requests or REST API endpoints without proper capability checks. A typical vulnerable pattern in WordPress plugins is:

// Vulnerable: No capability check
add_action('wp_ajax_nopriv_mailster_get_data', 'mailster_get_data');
function mailster_get_data() {
    // Process request without checking user permissions
    $data = get_option('mailster_settings');
    wp_send_json($data);
}

A patched version would include a capability check:

// Patched: Added capability check
add_action('wp_ajax_nopriv_mailster_get_data', 'mailster_get_data');
function mailster_get_data() {
    if (!current_user_can('manage_options')) {
        wp_die('Unauthorized', 403);
    }
    $data = get_option('mailster_settings');
    wp_send_json($data);
}

Exploitation & Lab Setup

Red Team

To simulate exploitation, set up a WordPress instance with WP Mailster version 1.8.16.0 installed and activated. Use the following steps:

1. Identify vulnerable endpoints: Use a tool like Burp Suite or curl to probe for unauthenticated access to plugin-specific endpoints.
2. Craft exploit request: Send a GET or POST request to a suspected vulnerable endpoint, such as /wp-admin/admin-ajax.php?action=mailster_get_data.
3. Verify unauthorized access: If the response contains sensitive data (e.g., subscriber emails, API keys), the vulnerability is confirmed.

Example curl command:

curl -v "http://target-site.com/wp-admin/admin-ajax.php?action=mailster_get_data"

Blue Team

To detect exploitation attempts, monitor for unusual requests to plugin-specific AJAX actions without authentication. Use the following detection rules:

• Web Server Logs: Look for requests to /wp-admin/admin-ajax.php with action parameters related to WP Mailster (e.g., mailster_*) from IPs not associated with authenticated users.
• IDS/IPS: Deploy rules to alert on unauthenticated access to these endpoints.

Indicators of Compromise (IOCs)

• URL Patterns: /wp-admin/admin-ajax.php?action=mailster_*
• HTTP Response: JSON responses containing sensitive plugin data (e.g., subscriber lists, settings)
• Source IPs: Unusual IPs making repeated requests to the above endpoints
• User Agents: Non-standard user agents (e.g., curl, python-requests)

Detection Engineering

YARA Rule

rule CVE_2024_53805_WP_Mailster_Missing_Auth {
    meta:
        description = "Detects exploitation attempts for CVE-2024-53805 in WP Mailster plugin"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2024-53805"
    strings:
        $ajax_action = "action=mailster_" ascii wide nocase
        $wp_admin = "/wp-admin/admin-ajax.php" ascii wide nocase
    condition:
        $ajax_action and $wp_admin
}

Sigma Rule

title: CVE-2024-53805 WP Mailster Missing Authorization Exploitation
id: 8a4b3c2d-1e5f-4a7b-9c8d-0e1f2a3b4c5d
status: experimental
description: Detects unauthenticated requests to WP Mailster AJAX endpoints
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'GET'
        cs-uri-query|contains: '/wp-admin/admin-ajax.php'
        cs-uri-query|contains: 'action=mailster_'
    condition: selection
falsepositives:
    - Legitimate authenticated users (rare)
level: high

Suricata Rule

alert http any any -> $HOME_NET any (
    msg:"CVE-2024-53805 WP Mailster Missing Authorization Exploit";
    flow:to_server,established;
    content:"/wp-admin/admin-ajax.php"; http_uri;
    content:"action=mailster_"; http_uri;
    classtype:attempted-recon;
    sid:1000001;
    rev:1;
    reference:cve,2024-53805;
)

Remediation & Mitigation

1. Immediate Action: Disable the WP Mailster plugin until a patch is available.
2. Vendor Update: Monitor the WordPress plugin repository for updates and apply the patch as soon as it is released.
3. Access Controls: Implement a Web Application Firewall (WAF) to block unauthenticated requests to plugin-specific endpoints.
4. Code Hardening: If you have access to the source code, add capability checks (e.g., current_user_can()) to all AJAX and REST endpoints.
5. Monitoring: Enable logging for all AJAX requests and review logs for suspicious activity.

Valters IT
Securing Digital Frontiers