CVE-2015-20121: RealtyScript SQL Injection Vulnerability

CVE-2015-20121 Overview

Next Click Ventures RealtyScript 4.0.2 contains SQL injection vulnerabilities that allow unauthenticated attackers to manipulate database queries by injecting arbitrary SQL code through the GET parameter u_id in /admin/users.php and the POST parameter agent[] in /admin/mailer.php. Attackers can exploit time-based blind SQL injection techniques to extract sensitive database information or cause denial of service through sleep-based payloads.

Critical Impact

Unauthenticated attackers can exploit these SQL injection flaws to extract sensitive database contents, bypass authentication mechanisms, or disrupt service availability through time-based blind SQL injection attacks.

Affected Products

• Next Click Ventures RealtyScript version 4.0.2
• RealtyScript /admin/users.php endpoint (via u_id GET parameter)
• RealtyScript /admin/mailer.php endpoint (via agent[] POST parameter)

Discovery Timeline

• 2026-03-16 - CVE-2015-20121 published to NVD
• 2026-03-18 - Last updated in NVD database

Technical Details for CVE-2015-20121

Vulnerability Analysis

This vulnerability represents a classic SQL Injection flaw (CWE-89) in the RealtyScript web application. The application fails to properly sanitize user-supplied input before incorporating it into SQL queries, allowing attackers to inject malicious SQL statements that alter the intended query logic.

Two distinct injection points exist within the administrative interface. The first resides in /admin/users.php, where the u_id GET parameter accepts unsanitized input. The second exists in /admin/mailer.php, where the agent[] POST parameter array similarly lacks proper input validation.

The time-based blind SQL injection technique allows attackers to infer database contents by observing response timing differences. By injecting payloads containing conditional SLEEP() functions, attackers can systematically extract data character by character based on whether the server response is delayed.

Root Cause

The root cause of this vulnerability stems from improper input validation and the direct concatenation of user-controlled input into SQL query strings. The application does not employ parameterized queries (prepared statements) or adequate input sanitization mechanisms, leaving the database layer exposed to manipulation through crafted input values.

Attack Vector

The attack is network-accessible and requires no authentication or user interaction. An attacker can craft malicious HTTP requests containing SQL injection payloads targeting either the u_id GET parameter or the agent[] POST parameter. Time-based blind injection allows data extraction even when the application does not directly display query results.

The exploitation typically involves sending requests with payloads like conditional sleep statements that cause measurable delays when specific conditions are true, enabling the attacker to infer database schema information, user credentials, and other sensitive data stored in the backend database.

Detection Methods for CVE-2015-20121

Indicators of Compromise

• Unusual HTTP requests to /admin/users.php containing SQL syntax in the u_id parameter
• POST requests to /admin/mailer.php with SQL injection payloads in agent[] parameter values
• Abnormally long response times from the application server indicating sleep-based blind SQL injection attempts
• Database query logs showing malformed or suspicious SQL statements with SLEEP(), BENCHMARK(), or timing functions

Detection Strategies

• Deploy Web Application Firewall (WAF) rules to detect and block SQL injection patterns in GET and POST parameters
• Implement application-layer logging to capture all requests to /admin/users.php and /admin/mailer.php endpoints
• Configure intrusion detection systems to alert on SQL injection signatures targeting known vulnerable parameters
• Monitor database query execution times for anomalous patterns indicative of time-based injection attacks

Monitoring Recommendations

• Enable detailed access logging on the web server to capture full request URIs and POST body contents
• Set up alerting for requests containing SQL keywords such as SELECT, UNION, SLEEP, or WAITFOR in parameter values
• Monitor for repeated requests from single IP addresses targeting administrative endpoints
• Implement real-time log analysis to detect potential exploitation attempts against these endpoints

How to Mitigate CVE-2015-20121

Immediate Actions Required

• Restrict access to administrative endpoints /admin/users.php and /admin/mailer.php using IP allowlisting or VPN requirements
• Deploy a Web Application Firewall with SQL injection detection rules to filter malicious requests
• If possible, take the vulnerable application offline until patches can be applied
• Review database access logs for signs of prior exploitation and compromised data

Patch Information

As of the last NVD update on 2026-03-18, no vendor patches have been publicly documented for this vulnerability. Organizations should contact Next Click Ventures directly for remediation guidance. Technical details are available in the Zero Science Vulnerability Report, Exploit-DB #38497, and the VulnCheck Advisory.

Workarounds

• Implement parameterized queries or prepared statements if modifying the source code is possible
• Add server-side input validation to reject requests containing SQL metacharacters in the u_id and agent[] parameters
• Use a reverse proxy or WAF to sanitize incoming requests before they reach the application
• Restrict database user privileges to minimize the impact of successful SQL injection attacks

# Example: Apache .htaccess to restrict admin access by IP
<Directory "/var/www/html/admin">
    Order Deny,Allow
    Deny from all
    Allow from 192.168.1.0/24
    Allow from 10.0.0.0/8
</Directory>