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Vulnerability Fixes

📅 March 10, 2026 ⏱️ 12 min read By VulnScan Security Team

SQL injection (SQLi) occurs when an attacker inserts malicious SQL code into an input field that gets executed by the database. If your application builds SQL queries by concatenating user input directly, it's vulnerable. Vulnerable code example:

// VULNERABLE - never do this
$query = "SELECT * FROM users WHERE username = '" + $_GET['user'] + "'";

If an attacker sends admin' OR '1'='1' -- as the username, the query becomes SELECT * FROM users WHERE username = 'admin' OR '1'='1' --', which returns all users.

Parameterized queries separate SQL code from data. The database driver handles escaping, making injection structurally impossible.

// SAFE - parameterized query (PHP/PDO)
$stmt = $pdo->prepare("SELECT * FROM users WHERE username = ?");
$stmt->execute([$username]);

// SAFE - parameterized query (Python)
cursor.execute("SELECT * FROM users WHERE username = %s", (username,))

// SAFE - parameterized query (Java)
PreparedStatement stmt = conn.prepareStatement("SELECT * FROM users WHERE username = ?");
stmt.setString(1, username);

Object-Relational Mappers (ORMs) like Eloquent (Laravel), Hibernate (Java), SQLAlchemy (Python), and Prisma (Node.js) use parameterized queries internally. Using an ORM correctly prevents most SQL injection by design.

// Laravel Eloquent - SAFE
$user = User::where('username', $username)->first();

// SQLAlchemy - SAFE
user = session.query(User).filter(User.username == username).first();

Never trust user input. Validate that inputs match expected formats before they reach your database layer. Use allowlisting (only permit known-good characters) rather than denylisting. For a username field: only allow alphanumeric characters and underscores. Reject any input containing quotes, semicolons, or SQL keywords.

Your web application's database user should only have the minimum permissions necessary. If your app only reads data, the database user should have SELECT privileges only — no INSERT, UPDATE, DELETE, or DROP. This limits the blast radius of a successful SQL injection attack. Even if an attacker injects SQL, they can only execute what the database user is permitted to do.

A WAF sitting in front of your application can detect and block SQL injection attempts before they reach your code. Major WAF providers include Cloudflare (free tier), AWS WAF, ModSecurity (open source), and Sucuri. Important: A WAF is defense-in-depth, not a replacement for secure code. Always fix the underlying SQL injection vulnerabilities.

After fixing SQL injection vulnerabilities, verify your fixes work. Use VulnScan's free SQL injection scanner to test your website from the outside — the same perspective an attacker uses. For developers, use OWASP ZAP or sqlmap in your CI/CD pipeline to automatically test for SQL injection on every code deployment.

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