CVE-2026-57640 Overview
CVE-2026-57640 is a broken access control vulnerability in the MasterStudy LMS Learning Management System plugin for WordPress. The flaw affects versions up to and including 3.7.30. An authenticated attacker holding only the Subscriber role can invoke plugin functionality that should be restricted to higher-privileged users. The weakness is categorized under CWE-862: Missing Authorization and enables unauthorized modification of application data.
Critical Impact
Authenticated subscribers can bypass authorization checks in MasterStudy LMS, allowing tampering with plugin-managed resources on affected WordPress installations.
Affected Products
- MasterStudy LMS Learning Management System plugin for WordPress
- Versions <= 3.7.30
- WordPress sites running the vulnerable plugin with subscriber-level registration enabled
Discovery Timeline
- 2026-06-26 - CVE-2026-57640 published to NVD
- 2026-06-26 - Last updated in NVD database
Technical Details for CVE-2026-57640
Vulnerability Analysis
CVE-2026-57640 is a Broken Access Control issue in MasterStudy LMS <= 3.7.30. The plugin exposes actions that fail to verify whether the requesting user holds an appropriate capability before executing sensitive operations. Because WordPress Subscribers are the lowest-privileged authenticated role, any site allowing open registration effectively exposes these actions to the public.
The integrity impact is limited: the flaw allows partial modification of data managed by the plugin without affecting confidentiality or availability. No user interaction is required beyond the attacker being logged in with a Subscriber-level account.
The issue tracks to CWE-862 Missing Authorization, where the application performs an action without checking that the caller is authorized. Additional context is available in the Patchstack Vulnerability Report.
Root Cause
The root cause is a missing capability check on one or more plugin endpoints. WordPress plugins are expected to gate privileged actions with current_user_can() verification and nonce validation. In vulnerable MasterStudy LMS builds, one or more handlers accept requests from any authenticated user, ignoring the intended role boundary between Subscribers and instructors or administrators.
Attack Vector
Exploitation occurs over the network against the WordPress admin-ajax or REST interface exposed by the plugin. An attacker registers or already possesses a Subscriber account. They then issue an authenticated HTTP request to the affected plugin endpoint. Because the endpoint omits authorization checks, the server processes the request and mutates plugin state that the Subscriber should not be able to change.
No public proof-of-concept exploit is currently available, and the vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog. The EPSS probability sits at 0.243%.
Detection Methods for CVE-2026-57640
Indicators of Compromise
- Authenticated HTTP POST requests to MasterStudy LMS AJAX or REST endpoints originating from accounts with the Subscriber role.
- Unexpected creation, modification, or deletion of LMS resources (courses, lessons, quizzes, user metadata) not attributable to instructor or admin accounts.
- Bursts of registration activity from new Subscriber accounts followed shortly by plugin API calls.
Detection Strategies
- Enable WordPress audit logging to capture the actor, capability, and endpoint for every plugin action, then alert on Subscriber-role users invoking MasterStudy LMS write operations.
- Correlate web server access logs against the plugin version banner to identify sites still exposing 3.7.30 or earlier.
- Review database change history for LMS tables and flag rows whose user_id maps to a low-privilege account.
Monitoring Recommendations
- Monitor /wp-admin/admin-ajax.php and /wp-json/ traffic for MasterStudy LMS action names invoked by non-instructor users.
- Track anomalous spikes in new Subscriber account registrations followed by plugin API interactions within a short time window.
- Alert on modifications to LMS content made outside normal instructor working hours.
How to Mitigate CVE-2026-57640
Immediate Actions Required
- Update the MasterStudy LMS Learning Management System plugin to a version newer than 3.7.30 as soon as a fixed release is available from the vendor.
- Audit all Subscriber-role accounts on affected WordPress sites and remove any that were created during suspicious registration bursts.
- Restrict user registration to trusted flows and require email verification for new accounts.
Patch Information
Refer to the Patchstack Vulnerability Report for the vendor's fixed version and remediation notes. Apply the update through the WordPress plugin manager or a controlled change-management process, then verify the plugin version post-deployment.
Workarounds
- Disable open user registration in WordPress Settings until the plugin is patched.
- Deploy a web application firewall rule that blocks Subscriber-role sessions from calling MasterStudy LMS write endpoints.
- Temporarily deactivate the MasterStudy LMS plugin on sites that cannot immediately restrict registration.
# Verify installed MasterStudy LMS version and disable registration via WP-CLI
wp plugin get masterstudy-lms-learning-management-system --field=version
wp option update users_can_register 0
wp plugin update masterstudy-lms-learning-management-system
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
