CVE-2026-39605: Super Custom Login Auth Bypass Flaw

CVE-2026-39605 Overview

A Missing Authorization vulnerability has been identified in the Obadiah Super Custom Login WordPress plugin (super-custom-login). This security flaw allows attackers to exploit incorrectly configured access control security levels, potentially enabling unauthorized access to protected functionality. The vulnerability stems from the plugin's failure to properly verify user permissions before allowing access to sensitive operations.

Critical Impact

Unauthorized users may bypass access controls and gain access to restricted plugin functionality, potentially compromising the WordPress login customization settings and related administrative features.

Affected Products

• Super Custom Login WordPress Plugin version 1.1 and earlier
• WordPress installations using the super-custom-login plugin

Discovery Timeline

• April 8, 2026 - CVE-2026-39605 published to NVD
• April 8, 2026 - Last updated in NVD database

Technical Details for CVE-2026-39605

Vulnerability Analysis

This vulnerability is classified as CWE-862 (Missing Authorization), which occurs when the software does not perform an authorization check when an actor attempts to access a resource or perform an action. In the context of the Super Custom Login plugin, the application fails to implement proper access control mechanisms, allowing unauthorized users to interact with functionality that should be restricted to privileged users only.

The Broken Access Control vulnerability allows attackers to exploit incorrectly configured security levels within the plugin. WordPress plugins that handle login customization typically require strict authorization checks to prevent unauthorized modification of authentication-related settings.

Root Cause

The root cause lies in the absence of proper capability checks within the plugin's code. WordPress provides functions such as current_user_can() to verify user permissions before executing privileged operations. The Super Custom Login plugin fails to implement these authorization checks adequately, creating a security gap that can be exploited.

When authorization checks are missing, any authenticated user—or in some cases, unauthenticated visitors—can access functionality intended only for administrators. This represents a fundamental design flaw in the plugin's access control architecture.

Attack Vector

An attacker could exploit this vulnerability by sending direct requests to the plugin's endpoints or AJAX handlers without proper authorization. Since the plugin does not verify that the requesting user has appropriate capabilities, these requests would be processed regardless of the user's actual privilege level.

The attack can be executed remotely through the network, potentially allowing low-privileged users to modify login page customizations or access sensitive configuration options. For detailed technical information, refer to the Patchstack Vulnerability Report.

Detection Methods for CVE-2026-39605

Indicators of Compromise

• Unexpected modifications to WordPress login page customizations
• Audit log entries showing unauthorized access to Super Custom Login settings
• Unusual requests to plugin-specific AJAX endpoints from low-privileged or unauthenticated users
• Changes to login branding or styling without corresponding administrative activity

Detection Strategies

• Review WordPress audit logs for access to Super Custom Login administrative functions by non-administrator users
• Monitor HTTP requests to plugin endpoints for suspicious patterns or unauthorized access attempts
• Implement web application firewall (WAF) rules to detect and block unauthorized access attempts
• Use WordPress security plugins that provide real-time monitoring of plugin activity

Monitoring Recommendations

• Enable comprehensive logging for all WordPress plugin activities
• Configure alerts for any changes to login customization settings
• Regularly audit user access patterns to administrative plugin endpoints
• Monitor for signs of privilege escalation or unauthorized configuration changes

How to Mitigate CVE-2026-39605

Immediate Actions Required

• Disable the Super Custom Login plugin until a patched version is available
• Review WordPress audit logs for any signs of exploitation
• Verify that login page customizations have not been tampered with
• Consider implementing additional access control measures at the server level

Patch Information

Organizations should monitor the Patchstack Vulnerability Report for updates regarding patches or fixed versions. Until an official patch is released, the plugin should be deactivated to prevent potential exploitation.

Workarounds

• Temporarily deactivate the Super Custom Login plugin from the WordPress admin dashboard
• Implement server-level access restrictions to plugin files using .htaccess or nginx configuration
• Use a Web Application Firewall (WAF) to block unauthorized requests to the plugin's endpoints
• Restrict WordPress administrative access to trusted IP addresses only

# Example: Restrict access to plugin directory via .htaccess
<Directory /var/www/html/wp-content/plugins/super-custom-login>
    Order Deny,Allow
    Deny from all
    Allow from 192.168.1.0/24
</Directory>