CVE-2024-53805: WP Mailster Auth Bypass Vulnerability

CVE-2024-53805 Overview

CVE-2024-53805 is a Missing Authorization vulnerability affecting the WP Mailster WordPress plugin developed by brandtoss. This broken access control flaw allows attackers to exploit incorrectly configured access control security levels, potentially granting unauthorized access to sensitive functionality within WordPress installations running vulnerable versions of the plugin.

The vulnerability stems from CWE-862 (Missing Authorization), indicating that the plugin fails to properly verify user permissions before allowing access to protected resources or functionality. This type of vulnerability is particularly dangerous in WordPress environments where plugins often handle sensitive operations like email management, subscriber data, and administrative functions.

Critical Impact

Unauthenticated attackers can exploit this broken access control vulnerability to bypass authorization checks and access restricted functionality in WP Mailster, potentially compromising site integrity, confidentiality, and availability.

Affected Products

• WP Mailster plugin for WordPress versions up to and including 1.8.16.0
• WordPress installations with vulnerable WP Mailster versions
• Any site using wpmailster:wp_mailster component

Discovery Timeline

• 2024-12-06 - CVE-2024-53805 published to NVD
• 2026-04-01 - Last updated in NVD database

Technical Details for CVE-2024-53805

Vulnerability Analysis

This vulnerability represents a fundamental failure in the authorization mechanism of the WP Mailster plugin. Missing authorization vulnerabilities occur when an application does not perform adequate permission checks before allowing users to access protected resources or execute sensitive operations.

In the context of WP Mailster, the plugin appears to expose functionality that should be restricted to authenticated administrators or authorized users to any visitor or lower-privileged user. This broken access control pattern can allow attackers to interact with newsletter management features, subscriber lists, email configurations, or administrative settings without proper authentication or authorization.

The network-accessible nature of this vulnerability means that remote attackers can exploit it without requiring any prior authentication or user interaction, making it trivially exploitable from anywhere on the internet.

Root Cause

The root cause of CVE-2024-53805 is the absence of proper authorization checks (CWE-862) within the WP Mailster plugin's codebase. WordPress plugins typically implement permission verification using capability checks such as current_user_can() or nonce validation to ensure that only authorized users can perform sensitive actions.

In vulnerable versions of WP Mailster (through 1.8.16.0), certain endpoints or AJAX handlers fail to implement these authorization controls, allowing any user—including unauthenticated visitors—to invoke protected functionality. This oversight in security design creates a significant access control gap that attackers can leverage.

Attack Vector

The attack vector for this vulnerability is network-based, requiring no privileges, no user interaction, and presenting low complexity for exploitation. An attacker can exploit this vulnerability by:

1. Identifying a WordPress site running a vulnerable version of WP Mailster
2. Crafting requests to the plugin's unprotected endpoints or AJAX handlers
3. Bypassing authorization controls to access restricted functionality
4. Potentially accessing subscriber data, modifying email configurations, or performing other privileged actions

The vulnerability mechanism involves sending specially crafted HTTP requests to the vulnerable plugin endpoints. Since no authorization checks are performed, the plugin processes these requests regardless of the user's authentication status or permission level. For detailed technical information, refer to the Patchstack Vulnerability Report.

Detection Methods for CVE-2024-53805

Indicators of Compromise

• Unusual HTTP requests to WP Mailster plugin endpoints from unauthenticated sources
• Unexpected modifications to newsletter settings or subscriber lists
• Access log entries showing direct calls to WP Mailster AJAX handlers without corresponding admin sessions
• Changes to email configuration settings without administrator activity

Detection Strategies

• Monitor WordPress access logs for suspicious requests targeting /wp-content/plugins/wp-mailster/ paths
• Implement Web Application Firewall (WAF) rules to detect and block unauthorized access attempts to plugin endpoints
• Review WordPress audit logs for unexpected changes to WP Mailster configurations
• Deploy endpoint detection solutions to identify exploitation attempts targeting broken access control vulnerabilities

Monitoring Recommendations

• Enable detailed logging for WordPress AJAX requests and plugin API calls
• Set up alerts for bulk access to subscriber data or email list exports
• Monitor for authentication bypass patterns in security information and event management (SIEM) systems
• Regularly audit user activity and permission changes within WordPress installations

How to Mitigate CVE-2024-53805

Immediate Actions Required

• Update WP Mailster plugin to a version newer than 1.8.16.0 immediately
• Conduct a security audit of WordPress installations to identify vulnerable plugin versions
• Review access logs for signs of prior exploitation attempts
• Temporarily disable the WP Mailster plugin if an immediate update is not possible

Patch Information

Organizations should update the WP Mailster plugin to the latest available version that addresses this broken access control vulnerability. The vulnerability affects all versions from the initial release through 1.8.16.0. Check the WordPress plugin repository or the vendor's official channels for the patched release.

For additional vulnerability details and remediation guidance, consult the Patchstack Vulnerability Report.

Workarounds

• Disable the WP Mailster plugin until a patched version can be installed
• Implement WAF rules to restrict access to WP Mailster plugin endpoints to authenticated administrators only
• Use WordPress security plugins to add additional access control layers around vulnerable functionality
• Restrict direct access to plugin directories via server configuration

# Apache .htaccess configuration to restrict plugin access
<Directory "/var/www/html/wp-content/plugins/wp-mailster">
    Order Deny,Allow
    Deny from all
    Allow from 127.0.0.1
    # Allow from your admin IP range
    # Allow from 192.168.1.0/24
</Directory>