Re: [Full-Disclosure] Multi-vendor AV gateway image inspection bypass vulnerability
On Mon, 10 Jan 2005 14:08:11 -0500, Darren Bounds
<dbounds@xxxxxxxxxxxxxx> wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> Multi-vendor AV gateway image inspection bypass vulnerability
> January 10, 2005
>
> A vulnerability has been discovered which allows a remote attacker to
> bypass anti-virus
> (as well other security technologies such as IDS and IPS) inspection of
> HTTP image content.
>
> By leveraging techniques described in RFC 2397 for base64 encoding
> image content within
> the URL scheme. A remote attack may encode a malicious image within the
> body of an HTML
> formatted document to circumvent content inspection.
>
> For example:
>
> http://www.k-otik.com/exploits/09222004.ms04-28-cmd.c.php
>
> The source code at the URL above will by default create a JPEG image
> that will attempt (and fail
> without tweaking) to exploit the Microsoft MS04-028 GDI+ vulnerability.
> The image itself is detected
> by all AV gateway engines tested (Trend, Sophos and McAfee), however,
> when the same image
> is base64 encoded using the technique described in RFC 2397 (documented
> below), inspection
> is not performed and is delivered rendered by the client.
>
> While Microsoft Internet Explorer does not support the RFC 2397 URL
> scheme; Firefox, Safari,
> Mozilla and Opera do and will render the data and thus successfully
> execute the payload if the necessary
> OS and/or application patches have not been applied.
>
> ## BEGIN HTML ##
>
> <html>
> <body>
> <img
> src="data:image/gif;base64,/9j/4AAQSkZJRgABAQEAYABgAAD//
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> Z">
> </body>
> </html>
>
> ## END HTML ##
>
> Solution:
>
> While AV vendor patches are not yet available, fixes for all currently
> known image vulnerabilities are
> and have been for several months. If you have not yet applied them,
> you have your own
> negligence to blame.
>
> Contributions:
>
> Thanks to Scott Roeder and Jacinto Rodriquez their assistance in
> platform testing.
I believe TrendMicro's OfficeScan (client-server scanner) will catch
it, but I am not sure about their gateway device. What was their
response?
...D