Local File Inclusion Vulnerabilities (LFI)

Malicious Local File Include Vulnerabilities

Local File Include (LFI) vulnerabilities are one of the most common and dangerous types of web application vulnerabilities. They allow an attacker to access and execute files on the server without authentication. This can lead to a variety of malicious activities, including remote code execution (RCE), privilege escalation, and data theft.

In this article, we will discuss what LFI vulnerabilities are, how they work, and how to prevent them. We will also provide examples of how to exploit LFI vulnerabilities to gain RCE vulnerabilities.

What is Local File Include Vulnerability?

Local File Include (LFI) is a type of vulnerability that allows an attacker to include and execute local files on the server. It is a type of injection attack that exploits the fact that the web application is not properly sanitizing user input.

The attacker can use this vulnerability to include and execute malicious code on the server, allowing them to gain access to sensitive information, escalate privileges, or even execute remote code.

How Does Local File Include Vulnerability Work?

When a web application is vulnerable to LFI, an attacker can use it to include and execute local files on the server. The attacker can do this by sending a specially crafted request to the web application.

The request contains a malicious file path that the web application will attempt to include and execute. If the web application is not properly sanitizing user input, the attacker can use this vulnerability to gain access to sensitive information, escalate privileges, or even execute remote code.

Examples of Exploiting Local File Include to Obtain RCE Vulnerabilities

An attacker can exploit LFI vulnerabilities to obtain RCE vulnerabilities in several ways.

One way is to use the “null byte” injection technique. This technique involves sending a specially crafted request to the web application that contains a malicious file path with a “null byte” character at the end. The web application will attempt to include and execute the malicious file, allowing the attacker to gain access to sensitive information or execute remote code.

Another way to exploit LFI vulnerabilities is to use the “double extension” technique. This technique involves sending a specially crafted request to the web application that contains a malicious file path with two extensions at the end. The web application will attempt to include and execute the malicious file, allowing the attacker to gain access to sensitive information or execute remote code.

Finally, an attacker can use the “relative path traversal” technique to exploit LFI vulnerabilities. This technique involves sending a specially crafted request to the web application that contains a malicious file path with relative path traversal characters. The web application will attempt to include and execute the malicious file, allowing the attacker to gain access to sensitive information or execute remote code.

Preventing Local File Include Vulnerabilities

There are several steps that can be taken to prevent LFI vulnerabilities.

First, it is important to ensure that all user input is properly sanitized. This can be done by using a whitelist of allowed characters and rejecting any input that does not match the whitelist.

Second, it is important to ensure that all requests are properly validated. This can be done by using a blacklist of forbidden characters and rejecting any requests that contain them.

Finally, it is important to ensure that all files are properly restricted. This can be done by using a strong file system permissions scheme and making sure that only authorized users have access to sensitive files.

Conclusion

Local File Include (LFI) vulnerabilities are one of the most common and dangerous types of web application vulnerabilities. They allow an attacker to include and execute local files on the server, allowing them to gain access to sensitive information, escalate privileges, or even execute remote code.

In this article, we discussed what LFI vulnerabilities are, how they work, and how to prevent them. We also provided examples of how to exploit LFI vulnerabilities to gain RCE vulnerabilities.

By following the steps outlined in this article, organizations can help protect themselves from LFI vulnerabilities and the malicious activities related to LFI

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