SUB 404 : A Fast Tool To Check Subdomain Takeover Vulnerability

Sub 404 is a tool written in python which is used to check possibility of subdomain takeover vulnerability and it is fast as it is Asynchronous.


During recon process you might get a lot of subdomains(e.g more than 10k). It is not possible to test each manually or with traditional requests or urllib method as it is very slow. Using Sub 404 you can automate this task in much faster way. Sub 404 uses aiohttp/asyncio which makes this tool asynchronous and faster.

How it works?

Sub 404 uses subdomains list from text file and checks for url of 404 Not Found status code and in addition it fetches CNAME(Canonical name) and removes those URL which have target domain name in CNAME. It also combines result from subfinder and sublist3r(subdomain enumeration tool) if you don’t have target subdomains as two is better than one. But for this sublist3r and subfinder tools must be installed in your system. Sub 404 is able to check 7K subdomains in less than 5 minutes.

Key Features

– Fast( as it is Asynchronous)
– Uses two more tool to increase efficiency
– Saves result in a text file for future reference
– Umm thats it, nothing much !

How to use?

Note: Only works on Python3.7+

Using Docker

As an alternative, it is also possible to build a Docker image, so no prerequisites are necessary.

$ docker build -t sub404 .
$ docker run –rm sub404 -h

Usage Example

Note: If subfinder and sublist3r is intalled.

  • This combines result from sublist3r and subfinder tool and checks for possibility of takeover.
    • $ python3 -d
  • If subfinder and sublist3r is not intalled, provide subdomains in text file
    • $ python3 -f subdomain.txt

Note: This tool is mostly tested in linux but should works on other OS too.

Usage Options

$ python3 -h

This will display help for the tool. Here are all the switches it supports.

-dDomain name of the taget.python3 -d
-fProvide location of subdomain file to check for takeover if subfinder is not installed.python3 -f subdomain.txt
-pSet protocol for requests. Default is “http”.python3 -f subdomain.txt -p https or python3 -d -p https
-oOutput unique subdomains of sublist3r and subfinder to text file. Default is “uniqueURL.txt”python3 -d -o output.txt
-hshow this help message and exitpython3 -h

Note: This tool fetches CNAME of 404 response code URL and removes all URL which have target domain in CNAME. So chan