Nginx Server Local File Inclusion Scanner

Nginx Server is widely used as a web server and reverse proxy server due to its high performance, stability, and low resource consumption. It is commonly used by web hosting providers, businesses, and developers to manage web applications and sites. Nginx supports load balancing, caching, and media file streaming, making it suitable for scaling web services. It is popular for serving dynamic web content and maintaining secure and optimized environments. Organizations often use Nginx as part of their infrastructure to manage traffic efficiently and ensure faster load times. Due to its broad adoption, vulnerabilities within Nginx can impact a wide range of web services.

Local File Inclusion (LFI) is a vulnerability that allows an attacker to include files on a server through web browser input. This vulnerability exploits insufficient input validation in web applications, allowing attackers to retrieve sensitive files located on the server. LFI can lead to exposure of sensitive information, execution of arbitrary code, or full server compromise if combined with other types of attacks. Being a critical security flaw, it is essential to identify and mitigate LFI vulnerabilities to protect sensitive server data. LFI vulnerabilities are prevalent in applications that allow file inclusion through URL parameters. Attackers may exploit this flaw to gain unauthorized access to application files or configurations.

The vulnerability in Nginx Server arises from the improper handling of URL slashes, allowing attackers to perform Local File Inclusion. By crafting specific requests with multiple slashes, attackers can access directories and files that should be restricted. The endpoint paths such as "{{BaseURL}}///////../../../etc/passwd" demonstrate how a malformed URL can target critical system files. This can bypass security controls intended to prevent unauthorized server file access. The vulnerable parameter is typically found in the URL path, enabling directory traversal attacks. Proper input validation and URL normalization are essential in preventing such vulnerabilities.

Exploitation of Local File Inclusion vulnerabilities can have severe consequences for organizations. Attackers may gain access to sensitive files such as configuration files, password files, or application code. This can lead to unauthorized data access, data exfiltration, or further exploitation through privilege escalation. Moreover, exposed files may provide attackers with information to launch additional attacks, compromising the entire system. In critical applications, this could disrupt services or result in the theft of sensitive user data. It is crucial to identify and rectify LFI vulnerabilities promptly to prevent potential breaches.

REFERENCES

• https://github.com/detectify/ugly-duckling/blob/master/modules/crowdsourced/nginx-merge-slashes-path-traversal.json
• https://medium.com/appsflyer/nginx-may-be-protecting-your-applications-from-traversal-attacks-without-you-even-knowing-b08f882fd43d