CWE-89: SQL Injection

Any SQL injection attack consists of insertion (or “injection”) of malicious code within the SQL command executed by the app. 

Effects of such malicious code injections can be unpredictable, depending on the attacker’s intelligence and SQL-interpreter’s characteristics, but the most common are:

• Read/modify sensitive data
• Execute administrative operations
• Execute commands on the underlying OS

Note: The most basic SQL injection attack is based on exploiting a dynamically constructed SQL query based on input data.

Let’s suppose an app that displays the user’s data based on the user’s name as typed from the application user in a web form.

Dynamically constructed SQL in-app code might look something like this: 

"select * from users where name = '" + userName + "'";

userName is user-supplied data that is directly inserted into the query and it will be sent to SQL-engine to be executed.

Let’s imagine the result when the attacker supplies the following text:

' or '1'='1

 In this case, SQL-engine will return all users’ data because 1=1 will always be TRUE.

This attack would the attacker be able to access users’ data (involving a privacy breach), but consequences can be more serious by combining query chaining with administrative commands such as

 Smith';drop table users; truncate audit_log;--by |

In this case, the attacker would be able to delete the users table or truncate system tables. Everything depends on the concrete case, but “the door is open” and, as you can imagine, imagination is the limit. How does the attacker know the app database tables? Depending on the error messages the application produces when a SQL injection attack happens, a smart attacker might be “inferring” database structure information from the error page. Discovering useful information is a matter of patience.

You could be thinking of a common app error management approach consisting of providing a generic error page, not displaying any exploitable information about the app’s internals.

Even in this case, the app is still vulnerable to SQL injection. Attackers can use a technique known as Blind SQL injection.

This hacking technique is based on asking the database questions and determines the answer based on the application's response. This attack is often used when the web application is configured to show generic error messages but has not mitigated the code that is vulnerable to SQL injection.

Some variants of SQL injection apply to specific frameworks or conditions:

• CWE-564: SQL injection: Hibernate
• CWE-566: Authorization Bypass Through User-Controlled SQL Primary Key

Further reading: Find further information on SQL injection at https://www.kiuwan.com/blog/SQL injection-avoid/.

SQL injection (CWE-89) coverage by Kiuwan

Kiuwan incorporates the following rules for SQL injection (CWE-89) for the following languages: