Eval injection

Sooraj V Nair
Published on
14 Nov 2023
5 min read

Eval injection is an injection technique by which an attacker can send a custom URL to the eval () function.

This capability extends to executing operating system commands. Here, the server does not properly validate user inputs in the page parameter.

A PHP language has a function that accepts a string and runs in the language. This function is known as eval ().

Eval injection, also known as “code injection” or “dynamic code execution,” is a security vulnerability that occurs when untrusted data is passed to an “eval ()” or similar function in a programming language.

This vulnerability allows an attacker to inject malicious code into a program or application, leading to various negative impacts.

What are the impacts of Eval injection?

The impacts depend on the context in which the eval injection occurs and the privileges granted to the code being executed.

Here are some of the potential impacts of eval injection:

1. Arbitrary code execution

The most significant impact of eval injection is the ability for an attacker to execute arbitrary code on the affected system.

This can result in full control over the application, allowing the attacker to perform unauthorized actions, steal sensitive data, or compromise the entire system.

2. Security bypass

Eval injection can bypass security controls and input validation mechanisms, as the injected code is executed by the application itself, often with elevated privileges.

3. Data breach or manipulation

Attackers can manipulate data by altering the intended behavior of the code being executed. This can lead to data corruption, unauthorized access, or data leaks.

4. Denial of Service (DoS)

In some cases, eval injection can be used to trigger resource-intensive operations, causing the application or system to consume excessive resources, leading to a DoS condition.

5. Escalation of privileges

If the eval injection occurs in a context with restricted privileges, the attacker can use it to escalate their privileges and gain access to sensitive areas or perform administrative actions.

6. Malware delivery

Eval injection can be used to deliver and execute malware on the targeted system, potentially infecting other connected systems or users.

7. Full control over the server

If an eval injection occurs in a web application, the attacker can compromise the web server, leading to a complete system compromise or unauthorized access to other web applications hosted on the same server.

8. Exploitation of database

The exploitation of eval injection can lead to the compromise of customer data, loss of trust, and damage to the reputation of the affected organization.

To prevent eval injection vulnerabilities, developers and system administrators should follow secure coding practices, such as avoiding the use of eval () functions whenever possible and using proper input validation and sanitization techniques.

Keeping software and libraries up to date with the latest security patches is also critical to avoid known vulnerabilities that could be exploited for eval injection attacks.

How can you prevent eval injection?

Eval injection is a type of code injection attack that occurs when an attacker can inject malicious code into a web application that is using the eval () function.

The eval () function takes a string of code as input and evaluates it as if it were written in the programming language of the web application.

This means that an attacker can inject malicious code into the web application and have it executed by the web server.

There are a number of ways to prevent or mitigate eval injection attacks. Some of the most common methods include:

1. Do not use the eval () function

This is the most effective way to prevent eval injection attacks.

However, in some cases, the eval () function may be necessary. If you must use the eval () function, you should take steps to sanitize the input that is passed to the function.

2. Use a parameterized query

A parameterized query is a query that uses parameters to represent the values that are being passed to the query.

This prevents an attacker from injecting malicious code into the query.

3. Use a web application firewall (WAF)

A WAF can help to filter out malicious traffic that could be used to exploit eval injection vulnerabilities.

4. Sanitize all user input

Before storing or processing user input, you should sanitize it to remove any potential malicious code. This will help to prevent eval injection attacks.

5. Keep your software up to date

You should regularly update your web application software with the latest security patches. This will help to protect your web application from known vulnerabilities.

6. Use a secure coding framework

A secure coding framework can help you to write code that is more resistant to attack.

7. Educate your developers

You should educate your developers about the risks of eval injection and how to prevent it.

8. Test your web application regularly

You should regularly test your web application for security vulnerabilities.

Beagle Security can help you identify and fix any vulnerabilities that could be exploited by an attacker.

By following these tips, you can help to reduce the risk of eval injection attacks and protect your web application from malicious activity.

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Written by
Sooraj V Nair
Sooraj V Nair
Cyber Security Engineer
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