Injection attacks are serious security threats to modern applications. These attacks target how applications, databases, and operating systems process input and allow attackers to insert malicious data and change the system's planned behavior. If input is not properly checked or sanitized, attackers can insert fake code or commands executed by the backend. This causes data leaks, privilege escalation, or complete system takeover. Injection vulnerabilities affect both old and new applications, making them a threat across all industries. To prevent these attacks, security engineers should prioritize secure coding, automated testing, and continuous monitoring.

This blog will talk about injection attacks and their types. Learn more about how they work and how to prevent them.

What is an Injection Attack?

An injection attack is a process performed by hackers by injecting malicious code into an application's execution flow via user-supplied data fields. The back-end system reads this data as code or directives and changes its behavior. The attack exploits systems if proper input validation is not applied and targets databases, operating systems, and interpreters. Injection attacks allow for unauthorized access, data manipulation, and remote command execution. These threats pose a serious risk to the system's confidentiality, integrity, and availability.

Types of Injection Attacks

Injection attacks vary based on the target system, interpreter, and query language. The way input is processed determines how each attack works. They change program logic, expose confidential information, or run unauthorized commands.

SQL Injection (SQLi)

Source: inside.wooster.edu

SQL injection changes database query logic by inserting malicious SQL code into input fields. It allows attackers to bypass authentication, access restricted records, and even delete entire tables. Poorly written queries that directly use user input are especially vulnerable. SQLi is one of the widely used attack types because of its simplicity and effectiveness. Security engineers should use parameterized queries rather than string concatenation while building SQL statements.

SELECT * FROM users WHERE username = 'admin' AND password = 'password123';
-- Malicious input: ' OR '1'='1
-- Modified query: SELECT * FROM users WHERE username = '' OR '1'='1';

Command Injection

Command injection takes advantage of an application's ability to execute internal commands. Attackers change input fields to run arbitrary commands on the server, which can result in data theft or a complete system takeover. This happens in poorly secured functions that build shell commands from unsanitized input. Command injection is unsafe in applications that need elevated privileges. Security engineers should avoid using direct shell execution and ensure that all inputs are strictly validated.

ping -c 1 192.168.0.1
-- Malicious input: 192.168.0.1; rm -rf /
-- Executed: ping -c 1 192.168.0.1; rm -rf

LDAP Injection

LDAP injection attacks happen when malicious input changes the LDAP queries used for authentication or directory lookups. When user input is not properly checked or sanitized, attackers can use LDAP injection to bypass authentication and gain unauthorized access to directory information. LDAP authentication is used in enterprise environments, which makes it an easy target. Injection happens when unauthorized data is directly injected into LDAP search queries to change the intended logic.  Use secure APIs with parameterized searches and strict input validation before putting any user input into LDAP filters to reduce these risks.

String userInput = request.getParameter("username");
String filter = "(&(uid=" + userInput + ")(userPassword=secret))";
ldapContext.search("ou=users,dc=example,dc=com", filter, searchControls);

XML Injection

Source: cobalt.io

XML injection exploits XML interpreter vulnerabilities by injecting invalid XML into input fields. This attack leads to data theft, provides unauthorized access, or disrupts the service. XML-based APIs and setups become vulnerable if they accept user input without validation. Implementing XML schema validation and deactivating external entity parsing can help prevent XML injections.

<user>
  <name>John</name>
</user>
-- Malicious input: <name><!ENTITY xxe SYSTEM "file:///etc/passwd"></name>

HTML Injection

HTML injection is the process of injecting raw HTML into application output, changing the way the page is produced. Attackers use HTML injection to change data, redirect users, or insert malicious code. It is similar to cross-site scripting (XSS) and affects structure rather than script execution.  Security engineers should prevent it by implementing strict input sanitization and proper output encoding.

<p>Welcome, John!</p>
-- Malicious input: <h1>Hacked</h1>
-- Output: <p>Welcome, <h1>Hacked</h1>!</p>

NoSQL Injection

NoSQL injection attacks document-based databases such as MongoDB, which use JSON queries. Improper handling of JSON input allows attackers to change searches, bypass authentication, or gain unauthorized access to data. To prevent NoSQL injection, security engineers should use strict schema validation and input type verification.

{ "username": "admin", "password": "admin123" }
-- Malicious input: { "username": { "$ne": null }, "password": { "$ne": null } }

XPath Injection

XPath injection changes the queries used to search XML documents. When user input is directly placed into XPath expressions, attackers can bypass authentication to gain sensitive information. XML-based applications which save or configure data are particularly vulnerable. Protection requires the use of prepared XPath expressions as well as input sanitization.

xpath = "//user[username='" + user + "' and password='" + pwd + "']"
result = xmlDoc.xpath(xpath)

How do Injection Attack Work?

Injection attacks change insufficient data and allow backend systems to run unwanted commands. These steps will explain how injection attacks work:

Accepts Inaccurate Input

Applications running on user input without validation are at risk. Forms, query parameters, headers, and API calls should be considered insecure data and reviewed before use. If validation checks are lacking or ineffective, attackers can inject payloads that are directly passed to backend components.

Embeds Input Directly in Queries

When user input is directly injected into dynamic SQL, shell commands, or directory lookups without sufficient encoding or parameterization, the intended behavior changes. The interpreter runs the injected code with the same privileges as the application.

Misread Malicious Code

Interpreters like SQL engines, shell command processors, or XML parsers don't understand valid instructions and injected payload. They see the malicious input as part of the logic and run it completely.

Change System Behavior

The inserted code running on the backend can change records, expose private information, or bypass authentication. The severity of the injection point applied in the application logic and the privileges of the target system help security engineers to know the impact.

Lack of Output Encoding

Even if input is reviewed, failure to use output encoding allows some injection attempts to succeed, particularly HTML or JavaScript-based injections. Rendering input without context-aware processing allows for the injection of markup, scripts, or instructions.

Execute Input With All Privileges

In many cases, the program runs with increased database or host operating system rights. When an injection happens, the malicious payload takes over all the rights and gives full access to attackers of data or system operations.

How to Prevent Injection Attacks?

Injection protection needs secure input processing, careful query building, and effective execution control. Here is how to prevent injection attacks:

Use Parameterized Queries

Always use parameterized queries to ensure that user input is considered as data rather than part of the query logic. This method prevents backend systems from interpreting input as executable code. Modern programming languages and database systems provide built-in support for prepared statements. Security engineers should avoid building queries by string concatenation because it exposes various vulnerabilities. Use parameterized queries to prevent SQL and NoSQL injection threats.

cursor.execute("SELECT * FROM users WHERE username = %s", (username,))

Validate All Inputs

Input validation helps to limit user permission on information types, lengths, and patterns. Security engineers should sanitize inputs by removing or rejecting any unwanted characters that have no place in certain fields. Use allowlists rather than denylists to ensure accuracy. Apply uniform validation on both the client and server sides. Invalid input should be rejected before it reaches any processing layers.

Apply Proper Output Encoding

The output encoding ensures that the browser or parser treats the input as data rather than code. Always encode according to the output context, like HTML, JavaScript, or XML. To prevent injection attacks, security engineers should separate HTML tags in web output an use dependable libraries that handle encoding automatically.

Avoid Dynamic Execution of Commands

Avoid creating dynamic commands or queries that combine user input.  Use secure APIs that keep arguments distinct from command logic. Shell injection works when commands are dynamically produced from raw input. This applies to both system commands and application scripts. Always choose static methods that require strict input control.

Enforce the Least Privilege Principle

Run programs and databases with only the rights they need.  Even if an attacker gets control, limit access to sensitive functions and data. Do not run backend services with administrative or full privileges. Give permissions to users for the operations that are needed to perform their tasks. This will help to reduce the effect of an injection attack.

Perform Regular Security Testing

Perform automated and manual testing to discover injection attacks in the application. Use static analysis tools, dynamic scanners, and runtime protections. Test all user input paths, like APIs, forms, headers, and third-party integrations. Regular testing helps discover vulnerabilities before they are exploited by attackers. Use security testing into CI/CD workflows to detect risks early.

Final Thoughts

Injection threats pose various risks to applications in every environment. They exploit weaknesses while programs are interpreting input and put the organization's data integrity, availability, and confidentiality at risk. Security engineers can maintain security by applying secure coding practices, properly validated input, and avoiding risky dynamic behaviors.

Akto is an API security platform that detects and prevents injection attacks by automated API security testing.  It continuously detects vulnerable endpoints, analyzes injection attack patterns, and monitors security measures.  Schedule a demo to learn how Akto can secure your APIs from injection attacks.