CVE-2026-39109: Apartment Visitors Management SQLi Flaw

CVE-2026-39109 Overview

A SQL Injection vulnerability exists in Apartment Visitors Management System V1.1 within the username parameter of the login page (index.php). This vulnerability allows an unauthenticated attacker to manipulate backend SQL queries during the authentication process and retrieve sensitive database contents. The flaw stems from improper input validation in the login functionality, enabling attackers to bypass authentication and potentially exfiltrate all stored data.

Critical Impact

Unauthenticated attackers can exploit this SQL injection to bypass authentication, extract sensitive visitor records, and potentially compromise the entire database without valid credentials.

Affected Products

• Apartment Visitors Management System V1.1
• PHP Gurukul Apartment Visitors Management System (PHP and MySQL)

Discovery Timeline

• 2026-04-20 - CVE-2026-39109 published to NVD
• 2026-04-20 - Last updated in NVD database

Technical Details for CVE-2026-39109

Vulnerability Analysis

This SQL Injection vulnerability (CWE-89) exists in the authentication mechanism of the Apartment Visitors Management System. The username parameter on the login page (index.php) does not properly sanitize user-supplied input before incorporating it into SQL queries. When a user submits login credentials, the application constructs a dynamic SQL query using the raw username value, creating a direct pathway for SQL injection attacks.

The vulnerability is particularly severe because it occurs in a pre-authentication context, meaning no credentials are required to exploit it. An attacker can craft malicious input containing SQL syntax that alters the intended query logic. This enables authentication bypass, where the attacker can log in as any user including administrators, as well as data extraction through UNION-based or blind SQL injection techniques to dump the entire database contents.

Root Cause

The root cause is the direct concatenation of user-supplied input into SQL queries without proper parameterization or sanitization. The application fails to use prepared statements with parameterized queries, which would separate SQL code from data. Additionally, there is no input validation to filter or escape special characters commonly used in SQL injection attacks such as single quotes, double dashes, and semicolons.

Attack Vector

The attack is network-based and requires no authentication or user interaction. An attacker sends a crafted HTTP POST request to index.php with a malicious payload in the username field. The payload typically includes SQL operators and clauses designed to manipulate the query execution. For example, classic authentication bypass payloads using OR-based logic or comment sequences can force the authentication query to return true regardless of the actual credentials provided.

The exploitation process involves submitting crafted SQL syntax in the username field of the login form. The malicious input is incorporated directly into the backend SQL query without sanitization. The modified query executes with attacker-controlled logic, allowing authentication bypass or data exfiltration depending on the payload used.

Detection Methods for CVE-2026-39109

Indicators of Compromise

• Unusual or malformed values in web server logs for the username parameter on index.php
• SQL syntax patterns in HTTP POST data including characters like single quotes, double dashes, UNION, SELECT, and OR statements
• Multiple failed authentication attempts followed by successful login from the same IP address
• Database query errors appearing in application logs or error responses

Detection Strategies

• Deploy Web Application Firewall (WAF) rules to detect and block SQL injection patterns in login form submissions
• Implement application-layer monitoring to flag requests containing common SQL injection keywords targeting the username parameter
• Enable database query logging to identify anomalous or unexpected queries executed during authentication
• Use SentinelOne Singularity to monitor for post-exploitation activities following successful SQL injection attacks

Monitoring Recommendations

• Monitor web server access logs for repeated requests to index.php with varying username payloads
• Set up alerts for database connections executing queries with unusual patterns during login events
• Track failed and successful authentication events correlation to identify potential bypass attempts
• Review application error logs for SQL syntax errors which may indicate probing activity

How to Mitigate CVE-2026-39109

Immediate Actions Required

• Restrict network access to the Apartment Visitors Management System to trusted IP ranges or place behind VPN
• Implement a Web Application Firewall with SQL injection detection rules as a protective layer
• Consider taking the application offline if it handles sensitive data until remediation is complete
• Audit database access logs for any evidence of prior exploitation or data exfiltration

Patch Information

No official vendor patch has been identified for this vulnerability at this time. Organizations using Apartment Visitors Management System V1.1 should contact PHP Gurukul for remediation guidance or implement the code-level fixes described in the workarounds. Technical details and vulnerability documentation are available from the GitHub CVE Repository and the PHP Gurukul Project Overview.

Workarounds

• Modify the index.php login code to use prepared statements with parameterized queries instead of string concatenation
• Implement strict input validation on the username field to allow only alphanumeric characters and reject SQL metacharacters
• Add rate limiting on the login endpoint to slow down automated injection attempts
• Deploy application-level escaping using PHP functions such as mysqli_real_escape_string() as a temporary measure until prepared statements are implemented

# Example: Block common SQL injection patterns using ModSecurity WAF rules
# Add to ModSecurity configuration
SecRule ARGS:username "@rx (?i)(union|select|insert|update|delete|drop|--|;|')" \
    "id:100001,phase:2,deny,status:403,msg:'SQL Injection attempt blocked in username'"