CVE-2021-24340: WP Statistics Auth Bypass Vulnerability

CVE-2021-24340 Overview

CVE-2021-24340 is a SQL Injection vulnerability affecting the WP Statistics WordPress plugin before version 13.0.8. The vulnerability arises from improper use of the WordPress esc_sql() function on a field that was not delimited by quotes, combined with a failure to properly prepare the query. Compounding this issue, an administrative page that should have been restricted was accessible to any visitor, including unauthenticated users, allowing remote attackers to exploit this flaw without authentication.

Critical Impact

This vulnerability allows unauthenticated remote attackers to execute arbitrary SQL queries against WordPress databases, potentially exposing sensitive information from over 600,000 affected sites.

Affected Products

• Veronalabs WP Statistics versions prior to 13.0.8
• WordPress installations running vulnerable WP Statistics plugin
• Sites using the WP Statistics plugin for visitor analytics

Discovery Timeline

• 2021-06-07 - CVE CVE-2021-24340 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2021-24340

Vulnerability Analysis

This SQL Injection vulnerability stems from a fundamental misunderstanding of WordPress security functions. The esc_sql() function in WordPress is designed to escape strings for use in SQL queries, but it only provides protection when the escaped value is properly enclosed in quotes within the SQL statement. When the vulnerable parameter is used without quote delimiters, the escaping becomes ineffective, allowing attackers to break out of the intended query structure and inject malicious SQL commands.

The second critical flaw is the exposure of an administrative-only page to unauthenticated users. This broken access control issue transforms what might have been a limited administrative vulnerability into a fully unauthenticated attack vector accessible to any remote attacker.

Root Cause

The root cause is twofold: first, the developers relied on esc_sql() without understanding its limitations when used with unquoted fields in SQL queries. WordPress provides the $wpdb->prepare() method specifically to handle parameterized queries safely, which was not utilized in this case. Second, improper access control allowed unauthenticated users to reach the vulnerable endpoint.

Attack Vector

The attack can be executed remotely over the network without requiring any authentication or user interaction. An attacker can craft malicious HTTP requests containing SQL injection payloads targeting the vulnerable parameter. Since the affected page is accessible to unauthenticated visitors, attackers can directly send exploitation requests to extract database contents, including sensitive user data, credentials, and other confidential information stored in the WordPress database.

The vulnerability specifically allows for data extraction (confidentiality impact) as the SQL injection enables arbitrary SELECT queries. The lack of proper query parameterization means attackers can leverage techniques such as UNION-based injection or time-based blind injection to exfiltrate database contents.

Detection Methods for CVE-2021-24340

Indicators of Compromise

• Unusual SQL-like patterns in web server access logs targeting WP Statistics endpoints
• Unexpected database queries or errors logged by WordPress or MySQL
• Access attempts to administrative WP Statistics pages from unauthenticated sessions
• Time-based delays in page responses that may indicate blind SQL injection attempts

Detection Strategies

• Monitor web application firewall (WAF) logs for SQL injection patterns in requests to WP Statistics URLs
• Implement database query logging and alert on unusual SELECT statements or query errors
• Review WordPress access logs for requests to /wp-admin/admin.php with page=wps_ parameters from unauthenticated sources
• Deploy intrusion detection rules that flag common SQL injection payloads in HTTP parameters

Monitoring Recommendations

• Enable WordPress debug logging to capture database errors that may indicate exploitation attempts
• Configure web server access logging with full request parameters for forensic analysis
• Set up real-time alerting for patterns associated with SQL injection testing tools
• Monitor database server performance metrics for unusual query patterns or load

How to Mitigate CVE-2021-24340

Immediate Actions Required

• Update WP Statistics plugin to version 13.0.8 or later immediately
• If update is not immediately possible, temporarily disable the WP Statistics plugin
• Review web server logs for evidence of exploitation attempts
• Audit database for potential data exfiltration if exploitation is suspected

Patch Information

The vulnerability was addressed in WP Statistics version 13.0.8. Users should update to this version or later through the WordPress plugin update mechanism. The fix properly implements parameterized queries using $wpdb->prepare() and restricts access to administrative pages to authenticated users with appropriate capabilities. Additional details can be found in the WPScan Vulnerability Report and the Wordfence Blog Analysis.

Workarounds

• Temporarily disable the WP Statistics plugin until the update can be applied
• Implement web application firewall rules to block SQL injection patterns targeting WP Statistics endpoints
• Restrict access to WordPress admin pages at the web server level if possible
• Use security plugins that provide virtual patching capabilities for known vulnerabilities

# Example: Disable WP Statistics plugin via WP-CLI
wp plugin deactivate wp-statistics

# After updating, verify the installed version
wp plugin get wp-statistics --field=version

# Update to the latest patched version
wp plugin update wp-statistics