CVE-2026-25308: Simple Membership Auth Bypass Vulnerability

CVE-2026-25308 Overview

CVE-2026-25308 is a Missing Authorization vulnerability affecting the Simple Membership WordPress plugin developed by wp.insider. This broken access control flaw allows authenticated attackers to exploit incorrectly configured access control security levels, potentially bypassing authorization checks that should restrict certain actions to privileged users.

Critical Impact

Authenticated attackers can bypass access control mechanisms in the Simple Membership plugin, potentially modifying membership settings or accessing restricted functionality without proper authorization.

Affected Products

• Simple Membership plugin versions up to and including 4.6.9
• WordPress sites using vulnerable Simple Membership configurations
• Sites with membership-based access control relying on this plugin

Discovery Timeline

• 2026-02-19 - CVE CVE-2026-25308 published to NVD
• 2026-02-19 - Last updated in NVD database

Technical Details for CVE-2026-25308

Vulnerability Analysis

This vulnerability stems from CWE-862 (Missing Authorization), a critical flaw category where the application fails to perform adequate authorization checks before allowing access to protected resources or functionality. In the context of the Simple Membership plugin, this manifests as inadequate verification of user permissions when certain actions are performed.

The flaw requires network access and low-privilege authentication, meaning an attacker needs a valid user account on the WordPress site to exploit it. Once authenticated, the attacker can perform actions that should be restricted to higher-privileged users, effectively bypassing the plugin's access control mechanisms.

The impact is primarily on data integrity, as unauthorized modifications can be made to membership settings or restricted content. While there is no direct impact on confidentiality or availability based on the vulnerability characteristics, the integrity compromise can lead to broader security issues in membership management workflows.

Root Cause

The root cause is the absence of proper authorization checks in one or more plugin functions. When a user makes a request to perform an action, the plugin fails to verify whether the authenticated user has the appropriate permissions to execute that specific operation. This is a common pattern in WordPress plugins where capability checks using functions like current_user_can() are either missing or improperly implemented.

Attack Vector

The attack is network-based, requiring the attacker to have low-privilege authentication (such as a subscriber or basic member account) on the target WordPress site. No user interaction is required from administrators or other users. The attacker sends crafted requests to the vulnerable plugin endpoints, which process the requests without verifying that the user has sufficient privileges.

The exploitation workflow involves:

1. Obtaining a low-privilege account on the target WordPress site
2. Identifying the vulnerable plugin endpoints that lack authorization checks
3. Sending requests to these endpoints to perform unauthorized actions
4. Bypassing membership restrictions or modifying protected settings

For technical implementation details regarding this vulnerability, refer to the Patchstack WordPress Plugin Advisory.

Detection Methods for CVE-2026-25308

Indicators of Compromise

• Unexpected changes to membership levels or access settings without corresponding admin activity
• Audit logs showing low-privilege users accessing administrative membership functions
• Modified membership configurations or user role assignments by non-administrator accounts
• Unusual POST requests to Simple Membership plugin endpoints from subscriber-level users

Detection Strategies

• Monitor WordPress access logs for requests to Simple Membership plugin endpoints from low-privilege authenticated sessions
• Implement file integrity monitoring to detect unauthorized changes to plugin files and membership database tables
• Review WordPress audit logs for membership setting modifications not performed by administrators
• Deploy web application firewall (WAF) rules to detect and block suspicious parameter manipulation attempts

Monitoring Recommendations

• Enable comprehensive logging for all Simple Membership plugin actions and user activities
• Configure alerts for membership configuration changes outside of normal administrative workflows
• Implement real-time monitoring for privilege escalation patterns in WordPress user sessions
• Regularly audit user permission assignments and membership level configurations

How to Mitigate CVE-2026-25308

Immediate Actions Required

• Update the Simple Membership plugin to a version newer than 4.6.9 when a patched version becomes available
• Review current membership configurations and user role assignments for unauthorized modifications
• Implement additional access control measures at the web server or WAF level as a defense-in-depth measure
• Audit existing user accounts and remove any suspicious or unnecessary low-privilege accounts

Patch Information

Organizations should monitor the Patchstack WordPress Plugin Advisory for updates regarding patched versions. Update to the latest version of Simple Membership as soon as a security fix is released by the plugin developers.

Workarounds

• Restrict plugin access by limiting registration and membership functionality to trusted users only
• Implement additional authorization checks using a security plugin or custom code to validate user capabilities
• Use a Web Application Firewall (WAF) to filter suspicious requests targeting plugin endpoints
• Temporarily disable the Simple Membership plugin if membership functionality is not critical until a patch is available

# WordPress configuration - restrict user registration
# Add to wp-config.php to limit exposure
define('DISALLOW_FILE_EDIT', true);

# Review and audit current user roles via WP-CLI
wp user list --role=subscriber --fields=ID,user_login,user_email

# Check plugin version
wp plugin list --name=simple-membership --fields=name,version,status