Tag Archives: mutation

Request encoding to bypass web application firewalls

I “think” I have discovered a “new” technique in bypassing external web application firewalls using request encoding. The idea is very simple but I had not seen this before to be used to bypass any protection mechanisms. Details of this technique has been published via NCC Group’s blog:

https://www.nccgroup.trust/uk/about-us/newsroom-and-events/blogs/2017/august/request-encoding-to-bypass-web-application-firewalls/

This technique was presented as one the methods to mutate the HTTP requests in:

There are loads of other anomalies that can be used to bypass WAFs using webservers behaviour in accepting HTTP requests; my plan is to complete this research and put all the results via the https://http.ninja/ website. Please feel free to contact me via my Twitter (@irsdl) if you have some ideas regarding this.

The unofficial PDF version of this blog post can be downloaded from here:
https://soroush.secproject.com/downloadable/request-encoding-to-bypass-web-application-firewalls.pdf

Almost all the cloud-based WAFs that I had tested could be bypassed using this technique at the time of discovery.