BypassFuzzer: Fuzz 401/403/404 pages for bypasses

by ddos · May 31, 2025

Bypass Fuzzer

Fuzz 401/403ing endpoints for bypasses

This tool performs various checks via headers, path normalization, verbs, etc. to attempt to bypass ACLs or URL validation.

It will output the response codes and length for each request, in a nicely organized, color-coded way so things are readable.

I implemented a “Smart Filter” that lets you mute responses that look the same after a certain number of times.

You can now feed it raw HTTP requests that you save to a file from Burp.

Download

git clone https://github.com/intrudir/BypassFuzzer.git

Use

Specifying a request to test

Best method: Feed it a raw HTTP request from Burp!

Simply paste the request into a file and run the script!

It will parse and use cookies & headers from the request.
The easiest way to authenticate your requests

python3 bypassfuzzer.py -r request.txt

Using other flags

Specify a URL

python3 bypassfuzzer.py -u http://example.com/test1/test2/test3/forbidden.html

Specify cookies to use in requests:

some examples:

–cookies “cookie1=blah“
-c “cookie1=blah; cookie2=blah“

Specify a method/verb and body data to send

bypassfuzzer.py -u https://example.com/forbidden -m POST -d “param1=blah&param2=blah2” 

bypassfuzzer.py -u https://example.com/forbidden -m PUT -d “param1=blah&param2=blah2”

Specify custom headers to use with every request Maybe you need to add some kind of auth header like Authorization: bearer <token>

Specify -H “header: value” for each additional header, you’d like to add:

bypassfuzzer.py -u https://example.com/forbidden -H “Some-Header: blah“ -H “Authorization: Bearer 1234567“

Smart filter feature!

Based on the response code and length. If it sees a response 8 times or more it will automatically mute it.

Repeats are changeable in the code until I add an option to specify it in a flag

NOTE: Can’t be used simultaneously with -hc or -hl (yet)

# toggle smart filter on
bypassfuzzer.py -u https://example.com/forbidden –smart

Specify a proxy to use

Useful if you wanna a proxy through Burp

bypassfuzzer.py -u https://example.com/forbidden –proxy http://127.0.0.1:8080

Skip sending header payloads or url payloads

[pastacode lang=”markup” message=”” highlight=”” provider=”manual” manual=”%23%20skip%20sending%20headers%20payloads%0Abypassfuzzer.py%20-u%20https%3A%2F%2Fexample.com%2Fforbidden%20-sh%0Abypassfuzzer.py%20-u%20https%3A%2F%2Fexample.com%2Fforbidden%20–skip-headers%0A%0A%23%20Skip%20sending%20path%20normailization%20payloads%0Abypassfuzzer.py%20-u%20https%3A%2F%2Fexample.com%2Fforbidden%20-su%0Abypassfuzzer.py%20-u%20https%3A%2F%2Fexample.com%2Fforbidden%20–skip-urls”/]

Hide response code/length

Provide comma-delimited lists without spaces. Examples:

[pastacode lang=”markup” message=”” highlight=”” provider=”manual” manual=”%23%20Hide%20response%20codes%0Abypassfuzzer.py%20-u%20https%3A%2F%2Fexample.com%2Fforbidden%20-hc%20403%2C404%2C400%20%20%0A%0A%23%20Hide%20response%20lengths%20of%20638%0Abypassfuzzer.py%20-u%20https%3A%2F%2Fexample.com%2Fforbidden%20-hl%20638%20%20″/]

Source: https://github.com/intrudir/