CVE-2026-40766 Overview
CVE-2026-40766 is a SQL injection vulnerability affecting the MasterStudy LMS Learning Management System plugin for WordPress in versions up to and including 3.7.25. The flaw allows authenticated users with subscriber-level privileges to inject arbitrary SQL into backend database queries. The weakness is classified under CWE-89: Improper Neutralization of Special Elements used in an SQL Command. Because subscriber accounts can typically be self-registered on WordPress sites running the plugin, the barrier to exploitation is low. Successful exploitation enables an attacker to read sensitive database contents and impact site availability through crafted queries.
Critical Impact
An authenticated subscriber can execute arbitrary SQL queries against the WordPress database, exposing confidential data and potentially disrupting LMS operations.
Affected Products
- MasterStudy LMS Learning Management System WordPress plugin
- All versions up to and including 3.7.25
- WordPress sites permitting subscriber-level registration with the plugin enabled
Discovery Timeline
- 2026-06-15 - CVE-2026-40766 published to NVD
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2026-40766
Vulnerability Analysis
The vulnerability resides in the MasterStudy LMS plugin's handling of user-supplied input within database queries accessible to authenticated subscribers. The plugin fails to properly sanitize or parameterize input before incorporating it into SQL statements. Attackers authenticated as subscribers can supply crafted payloads that alter query logic.
The issue produces a scope-changing impact, meaning the injected query can affect data and components beyond those normally accessible to a subscriber. According to the EPSS data published on 2026-06-18, the probability of exploitation in the next 30 days sits at 0.332% with a percentile rank of 24.844.
Root Cause
The root cause is missing parameterization of user input within at least one SQL query path reachable by subscriber-role users. WordPress provides $wpdb->prepare() for safe query construction, but the affected code path concatenates input directly into the SQL string. This permits operators such as UNION, OR, and stacked conditions to manipulate the resulting query.
Attack Vector
Exploitation requires network access to the WordPress site and an authenticated session at the subscriber role. The attacker registers or obtains a subscriber account, then submits a crafted HTTP request to a vulnerable plugin endpoint with SQL syntax embedded in a parameter. The backend executes the manipulated query against the WordPress database.
No user interaction is required beyond the attacker's own session. The vulnerability does not require administrative privileges, making it accessible to any registered user on affected sites.
Refer to the Patchstack Vulnerability Report for additional technical context.
Detection Methods for CVE-2026-40766
Indicators of Compromise
- Unexpected SQL syntax such as UNION SELECT, SLEEP(, or INFORMATION_SCHEMA in HTTP request parameters sent to MasterStudy LMS endpoints
- Authenticated subscriber accounts issuing high-frequency requests to plugin AJAX or REST routes
- Anomalous response sizes or response times from MasterStudy LMS endpoints suggesting blind or time-based injection
- New or modified rows in wp_users or wp_usermeta originating outside the standard administration workflow
Detection Strategies
- Inspect web server access logs for requests to MasterStudy LMS endpoints containing encoded SQL metacharacters such as %27, --, or %23
- Enable WordPress query logging or database audit logging to capture queries containing subscriber-supplied input
- Deploy a web application firewall rule set targeting SQL injection patterns on plugin URIs
- Correlate subscriber authentication events with subsequent plugin endpoint requests to identify low-privilege account abuse
Monitoring Recommendations
- Alert on subscriber-role accounts accessing plugin endpoints associated with course, quiz, or instructor data queries
- Track database error responses returned to authenticated low-privilege users
- Monitor creation of new subscriber accounts followed within minutes by repeated plugin endpoint requests
How to Mitigate CVE-2026-40766
Immediate Actions Required
- Update the MasterStudy LMS plugin to a release later than 3.7.25 once the vendor publishes a fixed version
- Audit existing subscriber accounts and remove any that were not legitimately registered
- Temporarily disable open user registration on sites that do not require it
- Review database query logs for evidence of prior exploitation attempts against plugin endpoints
Patch Information
Consult the Patchstack advisory for the latest fixed version and patch availability. Apply the vendor-supplied update through the WordPress plugin updater or by replacing plugin files directly. Verify the installed version after update via the WordPress administration plugins page.
Workarounds
- Deploy a web application firewall with SQL injection signatures applied to MasterStudy LMS request paths
- Restrict subscriber registration or require manual approval for new accounts until patching is complete
- Apply least-privilege database credentials so the WordPress database user cannot read sensitive tables outside the WordPress schema
- Disable the MasterStudy LMS plugin on sites where it is not actively required
# Example: disable open registration via wp-cli until patched
wp option update users_can_register 0
# Example: list and audit subscriber accounts
wp user list --role=subscriber --fields=ID,user_login,user_registered
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
