Bypassing URL Authentication and Authorization with HTTP Verb Tampering

["Arshan Dabirsiaghi" <arshan.dabirsiaghi () aspectsecurity com>]

Internetizens,

Many URL authentication and authorization mechanisms make security
decisions based on the HTTP verb in the request. Many of these
mechanisms work in a counter-intuitive way. This fact, in combination
with some oddities in the way that both web and application servers
handle unexpected HTTP verbs causes the rules dictated by those
mechanisms to be bypassable.

Many of us rely on the mechanisms I'm talking about. The Internet is not
exactly going to burn down when this email goes out, but there is
probably a fair number of externally facing web applications out there
that are relying on the shaky security provided by these configurations.

We have written a whitepaper that goes into some detail discussing the
vulnerability and how the various vendors are affected. You can grab the
whitepaper from Aspect Security's website:

http://www.aspectsecurity.com/documents/Bypassing_VBAAC_with_HTTP_Verb_T
ampering.pdf

Jeff Williams and Jim Manico also put together a demo that shows the
attack in progress:

http://www.aspectsecurity.com/documents/Aspect_VBAAC_Bypass.swf

Cheers,

Arshan Dabirsiaghi

Director of Research

Aspect Security

http://www.aspectsecurity.com/