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Example: Critical SQL Injection in Authentication Module

A detailed analysis of a SQL injection vulnerability discovered in a popular web framework's authentication system.

Overview

During a recent security assessment, we discovered a critical SQL injection vulnerability in the authentication module of a widely-used web framework. This vulnerability allows attackers to bypass authentication and potentially access sensitive user data.

Technical Details

The vulnerability exists in the login handler, where user input is directly concatenated into SQL queries without proper sanitization:

def authenticate(username, password):
    query = f"SELECT * FROM users WHERE username = '{username}' AND password = '{password}'"
    result = db.execute(query)
    return result.fetchone()

An attacker can exploit this by providing a malicious username:

username: admin'--
password: anything

This results in the following query:

SELECT * FROM users WHERE username = 'admin'--' AND password = 'anything'

The -- comments out the password check, allowing authentication as any user.

Impact

  • Severity: Critical (CVSS 9.8)
  • Attack Vector: Network
  • Authentication Required: None
  • User Interaction: None

An attacker can:

  1. Bypass authentication entirely
  2. Access any user account
  3. Extract sensitive data from the database
  4. Potentially execute arbitrary commands (depending on database configuration)

Mitigation

Use parameterized queries instead of string concatenation:

def authenticate(username, password):
    query = "SELECT * FROM users WHERE username = ? AND password = ?"
    result = db.execute(query, (username, password))
    return result.fetchone()

Timeline

  • 2025-01-15: Vulnerability discovered
  • 2025-01-16: Vendor notified
  • 2025-01-20: Vendor confirmed the issue
  • 2025-01-25: Patch released
  • 2025-01-30: Public disclosure

References