CVE-2026-4058: WordPress User Frontend Auth Bypass Flaw

CVE-2026-4058 Overview

CVE-2026-4058 affects the User Frontend WordPress plugin, which provides AI-powered frontend posting, user directory, profile, membership, and user registration features. The plugin contains a missing capability check on the user_subscription_cancel() function in all versions up to and including 4.3.2. Authenticated attackers with Subscriber-level access or higher can cancel any user's subscription pack, including those belonging to administrators. The flaw is classified as a broken access control issue [CWE-862].

Critical Impact

Low-privileged authenticated users can cancel arbitrary subscription packs across the site, disrupting paid memberships and administrator-managed subscriptions.

Affected Products

• User Frontend WordPress plugin versions up to and including 4.3.2
• WordPress sites running the AI Powered Frontend Posting, User Directory, Profile, Membership & User Registration plugin
• Any site permitting Subscriber-level or higher registration with the plugin enabled

Discovery Timeline

• 2026-06-09 - CVE-2026-4058 published to NVD
• 2026-06-09 - Last updated in NVD database

Technical Details for CVE-2026-4058

Vulnerability Analysis

The vulnerability resides in the user_subscription_cancel() function exposed by the User Frontend plugin. The function processes subscription cancellation requests without verifying whether the requesting user has the capability to cancel the targeted subscription. Because the function only validates that the request originates from an authenticated user, any account at the Subscriber tier or higher can submit cancellation requests for subscription packs owned by other users.

Exploitation requires a valid WordPress account but no further privileges. WordPress sites that allow open registration expose this functionality to any visitor willing to register. The attacker submits a crafted request referencing another user's subscription identifier, and the plugin processes the cancellation without an ownership or capability check.

The impact is limited to integrity of subscription data. Confidentiality and availability of the broader site are not directly affected. However, mass cancellation of paid memberships disrupts revenue, content access, and administrator subscription state.

Root Cause

The root cause is a missing authorization check [CWE-862] inside user_subscription_cancel(). The handler does not call current_user_can() or equivalent capability validation, nor does it confirm that the subscription identifier in the request belongs to the requesting user.

Attack Vector

An authenticated attacker sends a request to the plugin's subscription cancellation endpoint with a target subscription identifier. The plugin executes the cancellation regardless of subscription ownership. Refer to the Wordfence Vulnerability Report for additional technical context.

Detection Methods for CVE-2026-4058

Indicators of Compromise

• Unexpected subscription cancellations in the plugin's subscription logs or WordPress database tables
• Subscriber-level accounts issuing POST requests to the plugin's subscription cancellation endpoint
• Administrator or premium-tier subscription packs transitioning to cancelled status outside of normal user activity
• Spike in account registrations followed shortly by cancellation requests

Detection Strategies

• Audit web server access logs for requests targeting user_subscription_cancel actions originating from low-privileged accounts
• Compare subscription state changes against user activity in WordPress audit logs to identify cross-user cancellations
• Alert on cancellation requests where the authenticated user ID does not match the subscription owner

Monitoring Recommendations

• Enable WordPress audit logging for subscription state transitions and capability-sensitive AJAX actions
• Monitor for new Subscriber-level account creation followed by immediate subscription endpoint activity
• Track HTTP 200 responses to cancellation endpoints from accounts that do not own active subscriptions

How to Mitigate CVE-2026-4058

Immediate Actions Required

• Update the User Frontend plugin to a version newer than 4.3.2 that includes the capability check fix
• Review subscription records for unauthorized cancellations dating back to the plugin's installation
• Restrict open user registration until the plugin is patched, or temporarily disable the plugin

Patch Information

The vendor addressed the missing capability check in the plugin source code. Review the WordPress Changeset Update for the specific commit that introduces the authorization check inside user_subscription_cancel(). Apply the fixed release through the WordPress plugin updater.

Workarounds

• Disable the User Frontend plugin until the patched version is deployed
• Temporarily remove the Subscriber role's ability to register on the site to reduce the attacker pool
• Place the site behind a web application firewall rule that blocks requests to the subscription cancellation action from non-owner users

# Configuration example
wp plugin update wp-user-frontend --version=latest
wp option update users_can_register 0