Nginx alias traversal sample app

There is a vulnerability in Nginx that can be caused by misconfiguration. One of them is alias traversal.

How to use

Dockerfile exists. Sample app work on any port.

$ docker build -t nginx-traversal .
$ docker run -d -p 127.0.0.1:3000:80 nginx-traversal:latest

Tools to find

Gixy is a tool to analyze Nginx configuration.

$ gixy vulnerable.conf 

==================== Results ===================

>> Problem: [alias_traversal] Path traversal via misconfigured alias.
Description: Using alias in a prefixed location that doesn't ends with directory separator could lead to path traversal vulnerability. 
Additional info: https://github.com/yandex/gixy/blob/master/docs/en/plugins/aliastraversal.md
Pseudo config:

server {
	server_name localhost;

	location /static {
		alias /var/www/app/static/;
	}
}

==================== Summary ===================
Total issues:
    Unspecified: 0
    Low: 0
    Medium: 0
    High: 1

Also, burp extention exists.

• PortSwigger/nginx-alias-traversal: Burp extension to detect alias traversal via NGINX misconfiguration at scale.

Case Study

• #312510 [mobs.mail.ru] nginx path traversal via misconfigured alias
• #317201 [vulners.com] nginx alias_traversal

Licence

The MIT License