OSEC

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Re: McAfee Web Gateway URL Filtering Bypass

From: Vikram Dhillon (dhillonv10gmail.com)
Date: Sat Apr 21 2012 - 07:40:09 CDT


Hello,

We might be able to fix this by simply doing a ping to the website
before connecting, so that the IP of the host specified matches the
connect field. In any case, the consistency of the host and connect is
indeed a big design flaw.

- Vikram

On Mon, Apr 16, 2012 at 6:12 PM, Gabriel Menezes Nunes
<gab.mnunesgmail.com> wrote:
> # Exploit Title: McAfee Web Gateway URL Filtering Bypass
> # Date: 16/04/2012
> # Author: Gabriel Menezes Nunes
> # Version: McAfee Web Gateway
> # Tested on: McAfee Web Gateway 7.0
> # CVE: CVE-2012-2212
>
>
> I found a vulnerability in McAfee Web Gateway 7 that allows access to
> filtered sites.
> The appliance believes in the Host field of HTTP Header using CONNECT method.
> Example
>
> CONNECT 66.220.147.44:443 HTTP/1.1
> Host: www.facebook.com
>
>
> It is blocked.
>
> CONNECT 66.220.147.44:443 HTTP/1.1 (without host field)
>
> It is blocked.
>
> But:
>
> CONNECT 66.220.147.44:443 HTTP/1.1
> Host: www.uol.com.br (allowed url)
>
> The connection works.
>
> From here, I can send SSL traffic without a problem. This way, I can
> access any blocked site that allows SSL connections.
> Others test that I did is convert GET methods in CONNECT methods.
>
> GET http://www.facebook.com HTTP/1.1
> Host: www.facebook.com
>
> in
>
> CONNECT 66.220.147.44:80 HTTP/1.1
> Host: www.uol.com.br
>
> It will connect.
>
> and after it is possible to send the GET packets. It will work!
>
> This vulnerability is different from the CONNECT Tunnel method. The
> flaw is on the Host field processing. The appliance believes on this
> field.
>
> So, any sites can be accessed. URL filtering in this device/software
> is irrelevant and useless.
> One of the most important (if not the most important) feature of this
> kind of device is to protect the network in accessing specific URLs.
> So, this flaw is very dangerous, and it can be implemented even in
> malwares, bypassing any protection.
> I developed a python script that acts like a proxy and it uses this
> flaw to access any site.
> This tool is just a proof of concept.

--
Regards,
Vikram Dhillon

~~~
To perceive is to suffer.