From: ViPeR (viper31337yahoo.co.in)
Date: Tue Dec 07 2004 - 06:19:35 CST

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Affected Software : Microsoft Internet Explorer
Vulnerability : Local File Detection

Tested On : MS IE 6.0 SP1, Win2K SP4, [up-to-date]
according to windowsupdate.com

Discovered by : Gregory R. Panakkal

Overview
========
This security vulnerability in Internet Explorer
allows remote attackers to discover what software is
installed on the remote computer, by testing for the
existence of certain files.

The "sysimage://" protocol is used to display the
appropriate icon corresponding to a file path when
viewed from MSIE. The default behaviour is such, that
if a existing file-path is given as input, it displays
the approritate icon [as described above], but if the
file-path supplied doesn't exists, it loads the icon
of a folder instead [ie, it gives out no error].

But as always, there is a way to bypass it.. and let
us differentiate between a valid path and an invalid
one, and thus using the onLoad and onError event
handlers, the 'local file detection' is a piece of
cake.

There isn't much of a documentation on the net
regarding the "sysimage://", atleast google didn't
show up anything useful :(

Proof Of Concept
================

<img src="sysimage://C:\WINNT\Notepad.exe,666"
onLoad="document.write('<b>Cannot Find File!</b>');"
onError="document.write('<b>File Exists!</b>');">

Demo
====

A demonstration is available at the following URL.

http://crapware.lx.ro/junkcode/security/ie-sp1-sysimage-local-file-existence.htm

Greetz to
=========
Liu Die Yu, Rakesh Balasunder

rgds,
Gregory R. Panakkal
(aka JunkCode / Viper)

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