Full Disclosure mailing list archives

Re: Multi-vendor AV gateway image inspection bypass vulnerability

From: Steven Rakick <stevenrakick () yahoo com>
Date: Wed, 12 Jan 2005 12:37:42 -0800 (PST)

This would mean that if an image exploiting the
recently announced Microsoft LoadImage API overflow
were imbedded into HTML email there would be zero
defense from the network layer as it would be
completely invisible.

Why am I not seeing more about this in the press? It
seems pretty threatening to me...

On Tue, 11 Jan 2005 14:58:43 -0500, Darren Bounds
<lists () intrusense com> wrote:

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 () intrusense com> 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
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Iy
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xAAfAAABBQEBAQEBAQAAAAAAAAAA
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xAC1EAACAQMDAgQDBQUEBAAAAX0BAgMABBEFEiExQQYTUWEHInEUMoGR

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=== message truncated ===



                
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Current thread:

Multi-vendor AV gateway image inspection bypass vulnerability Darren Bounds (Jan 10)
- Re: Multi-vendor AV gateway image inspection bypass vulnerability Jeff Gillian (Jan 11)
  - Re: Multi-vendor AV gateway image inspection bypass vulnerability - KMail Noam Rathaus (Jan 12)
- Re: Multi-vendor AV gateway image inspection bypass vulnerability Danny (Jan 11)
  - Re: Multi-vendor AV gateway image inspection bypass vulnerability Darren Bounds (Jan 11)
- <Possible follow-ups>
- Re: Multi-vendor AV gateway image inspection bypass vulnerability Steven Rakick (Jan 11)
- Re: Multi-vendor AV gateway image inspection bypass vulnerability Steven Rakick (Jan 12)
  - Re: Multi-vendor AV gateway image inspection bypass vulnerability Nils Ketelsen (Jan 12)
  - Re: Multi-vendor AV gateway image inspection bypass vulnerability Frank Knobbe (Jan 12)
    - Re: Multi-vendor AV gateway image inspection bypass vulnerability Steven Rakick (Jan 12)
    - Re: Multi-vendor AV gateway image inspection bypass vulnerability Frank Knobbe (Jan 12)