Input validation attack is a form of cyber attack where threat actors type a malicious input into a system. The input can be a piece of code, a script, or a command, which the target system then executes. As a result, threat actors can damage the system and access, copy, and manipulate sensitive information.

The cyber attack takes advantage of a vulnerability in applications and systems where user input is not thoroughly filtered and validated. Such a vulnerability creates an opportunity for malicious actors to exploit the system. An input validation attack falls under the injection vulnerability umbrella, one of the top 10 web application security risks named by the Open Web Application Security Project (OWASP) Foundation.


Read More about an Input Validation Attack

Threat actors always look for cracks that would allow them to enter a system and wreak havoc. An example of a tiny and common fissure that cybercriminals can exploit is input validation. We talk more about input validation, an input validation attack, and related concepts below.

What Is Input Validation?

Users are allowed to input data into most applications. For example, when purchasing items from an e-commerce platform, users are asked to type in their credit card numbers. Part of the input validation process will be to check if the user input only contains numbers. The e-commerce platform is also programmed to check that the input is 13–16 digits long. 

What Are the Types of User Input?

User input can come in different forms. Users can type alphabetic, numeric, or alphanumeric characters. They can also input symbols as part of text strings. In most instances, web applications also allow users to select a value from predefined choices through dropdowns or checkboxes.

The table below shows the most common types of input and their examples.

User Input TypeExample
StringPassword: p@sswoRd
NumberAge: 30
Enumeration (enum)Age range: 18–25
QueryGender: Male, Female
BooleanEmployment status checkbox:  Currently employed

Enum, query, and boolean input types can be locked so users cannot override predefined values. However, strings and numbers have to be validated to avoid exploitation.

What Are the Types of Input Validation Attacks?

The most common input validation attacks are:

  • Buffer overflow attacks: This attack occurs when threat actors feed an application input that its buffer or memory storage cannot handle. The overflow makes the system unresponsive since the malicious input consumes a considerable part of the application’s memory.
  • Canonicalization attacks: In canonicalization attacks, malicious actors use a file’s canonical name (CNAME) to gain unauthorized access to web server directories. The CNAME can be typed into an input field or as part of the URL.
  • XSS attacks: An XSS attack happens when threat actors inject malicious scripts into websites so the code is executed in a website visitor’s browser. This tactic enables the attacker to masquerade as the user.
  • SQLi attacks: Like XSS attacks, SQLi attackers inject malicious code using the SQL programming language. The goal is for threat actors to gain access to the application’s backend database.

How to Prevent an Input Validation Attack

There are sophisticated methods of protecting applications, systems, and businesses from cyber attacks. These security processes include creating data backups, using the latest industry-standard encryption methods, and investing in reliable cybersecurity solutions.

But an input validation attack can be avoided if software developers employ secure coding practices, such as:

  • Limiting the input size to minimize the number of weapons attackers can use. For instance, a name field may be set to allow up to 90 characters only, while the age field can be limited to three characters.
  • Defining allowable values instead of accepting all values and defining exceptions. For example, it’s safer to disallow all values except uppercase and lowercase letters rather than allowing all values except symbols that can help execute code.
  • Use input filtering and validation libraries that other seasoned developers have written and tested.
  • Conduct penetration testing on web applications and programs to cover as many cracks as possible.

Key Takeaways

  • An input validation attack is a dangerous form of cyber attack where threat actors manipulate the input field to damage an application or access its sensitive data.
  • The attack exploits vulnerabilities in a system’s input validation process, such as failing to restrict input size or defining a massive range of allowable characters. 
  • An input validation attack is an injection vulnerability found on OWASP’s top 10 web application security risks.
  • The most common types of input validation attacks are buffer overflow, canonicalization, cross-site scripting (XSS), and SQL injection (SQLi) attacks.
  • To prevent an input validation attack, software developers must employ coding best practices from the get-go.
  • Penetration testing can help detect input validation vulnerabilities.