What are injection flaws?

Key takeaways:

• Injection flaws occur when untrusted input is improperly handled, allowing attackers to inject malicious commands into  applications, databases, or operating systems.

• Attackers exploit weak input validation to execute unauthorized actions like accessing sensitive data, bypassing authentication, or even running malicious code remotely.

• Implement strict input validation, sanitize special characters, apply the principle of least privilege, and use prepared statements or parameterized queries to effectively prevent injection attacks.

Common types of injection flaws

How injection flaws work

Injection flaws occur when user inputs are processed by the application code without proper input validation or sanitization, resulting in data breaches, system compromises, or complete control of the application. These attacks generally follow a recognizable pattern that can be broken down into the following key steps:

1. User input: The attacker provides input to the application, often through user interface elements like forms, URLs, or APIs that are not properly validated or sanitized.

2. Code construction: The application processes the input and dynamically constructs a code command using the user-supplied data without sufficient validation.

3. Code execution: The application executes the application logic and interprets the user-provided input as part of the code instead of data, allowing the attacker to manipulate the intended behavior of the application.

4. Unauthorized access: The execution of the malicious code leads to unauthorized access, such as data exposure, data modification, or execution of commands that grant attackers the privilege to perform administrative actions.

5. Exploitation: The attacker leverages the successful execution of the injected code to exploit vulnerabilities in different ways, depending on the target system and application functionality. This can involve stealing data, bypassing authentication, executing remote code, or launching other attacks—each with potentially serious consequences.

Sample SQL injection implementation

SQL injection is one of the most common and dangerous injection attacks. It occurs when an attacker manipulates a SQL query by inserting malicious input, allowing him to read or modify sensitive information in the database.

The following command can be added to access an account of a user using SQL injection.

In the password column, type:

The backend SQL command is:

Here, when the user adds the value or email and password, the command becomes:

Since the above command contains 1==1, which is always true, the system grants access to the email abc@h.com.

How to prevent injection attacks

There are many ways to protect against an Injection flaw:

1. Input validation: Check that the input is similar to what is expected, e.g., J\ is not a valid name and, therefore, < and similar characters should not be allowed.

2. Input sanitization: Certain characters such as ' are allowed within names. Thus, these characters should be encoded before transmitting to the backend, e.g., John O’Leary must be transmitted as John O%27Leary if URL encoding is used. This would ensure that the database does not treat ′ as an ending quote, but rather as a string. However, it is important to decode the string before it’s displayed on the screen.

3. Implement least privilege: Granting only the minimum permissions necessary can be very effective in protecting against injection flaws and limiting their impact. Experts recommend implementing the principle of least privilege as part of a broader security strategy to provide strong protection against injection flaws. For example, if an attacker manages to exploit an injection flaw, the damage can be reduced by having the compromised account or process be isolated with minimal permissions.

4. Tools: Make use of tools and frameworks to prepare statements that prevent such attacks.

The following statements are applicable in Java, PHP, SQL, and many other languages. The following suggests how to use Prepared Statements.

This automatically applies validation on usernames and prevents any invalid characters. The syntax also prevents hackers from gaining access to other unauthorized information.

Conclusion

One of the most significant security flaws in online applications is still injection flaws. Attackers use them to execute malicious code that allows them to read or alter data and gain unauthorized access to systems. To counter these attacks, developers are recommended to employ prepared statements or stored procedures, output encoding, input validation, and other defenses to keep applications safe and greatly reduce the chance of becoming the victim of injection attacks.