Unreal Game Engine UMOD '..\' Input Validation Flaw Lets Remote Users Overwrite Files on the Target System
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SecurityTracker Alert ID: 1009923
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CVE Reference: GENERIC-MAP-NOMATCH
(Links to External Site)
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Updated: Apr 26 2004
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Original Entry Date: Apr 23 2004
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Impact: Modification of system information, Modification of user information
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Exploit Included: Yes
Vendor Confirmed: Yes
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Description: Luigi Auriemma reported a vulnerability in the Unreal game engine. A remote user can overwrite files on the target system.
It is reported that a remote user can create a specially crafted filename containing the '..\' directory traversal characters as
part of an Unreal MOD (UMOD) archive file to cause the target system to overwrite arbitrary files on the target system when installing
the archive.
A demonstration exploit is available at:
http://aluigi.altervista.org/poc/umodpoc.zip
The vendor was reportedly
notified on December 18, 2003.
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Impact: A remote user can create an update file that, when installed, will overwrite files on the target user's system with the privileges of the target user.
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Solution: The report indicates that the Unreal Tournament 2004 game (using the Unreal engine) was fixed prior to release, but that Unreal Tournament
and Unreal Tournament 2003 are still vulnerable. An unknown number of other games that use the Unreal engine may be affected.
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Vendor URL: unreal.epicgames.com/ (Links to External Site)
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Cause: Input validation error
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Underlying OS: MacOS, UNIX (OS X), Windows (Any)
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Underlying OS Comments: The affected UMOD function is not officially supported on Linux platforms
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Reported By: Luigi Auriemma <aluigi@altervista.org>
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Message History:
None.
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Source Message Contents
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Date: Thu, 22 Apr 2004 18:02:20 +0000
From: Luigi Auriemma <aluigi@altervista.org>
Subject: Arbitrary file overwriting in Unreal engine through UMOD
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#######################################################################
Luigi Auriemma
Application: Unreal engine
http://unreal.epicgames.com
Versions: any game based on this engine that supports the UMOD
installation.
An example are Unreal Tournament <= 451b and Unreal
Tournament 2003 <= 2225.
A full list of vulnerable games is not available.
Platforms: Windows and MacOS (on Linux the UMODs are not officially
supported)
Bug: arbitrary file overwriting
Risk: medium as diffusion but critical as damage
Exploitation: local
Date: 22 Apr 2004
Author: Luigi Auriemma
e-mail: aluigi@altervista.org
web: http://aluigi.altervista.org
#######################################################################
1) Introduction
2) Bug
3) The Code
4) Fix
#######################################################################
===============
1) Introduction
===============
The Unreal engine developed by EpicGames natively supports a file
format called UMOD used to easily install external add-ons:
"Umod: (aka Unreal MOD) Platform independent archives that allow mod
authors to ship their game content to unreal engine gamers"
#######################################################################
======
2) Bug
======
The UMOD file format is a simple archive that contains all the files to
install plus a manifest.ini file read by the UMOD installer and used to
know some informations as the author of the mod, the description, the
needed minimum game version and more.
Using the classical "..\" pattern in the filename and in its name into
the manifest.ini file an attacker is able to go outside the game's
directory and to overwrite ANY file in the partition on which the game
is installed, without alerts or messages from the installer.
#######################################################################
===========
3) The Code
===========
http://aluigi.altervista.org/poc/umodpoc.zip
However is also possible create a normal UMOD file using the specific
utilities commonly used to do it as UmodWizard, modifying a filename
and its name in the manifest.ini file using the "..\" pattern just as
"..\..\..\windows\notepad.exe" and then recalculating the checksum of
the package with the -C option of my UMOD extractor utility
http://aluigi.altervista.org/papers/umodext.zip.
#######################################################################
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4) Fix
======
The bug has been signaled to EpicGames the 18 December 2003.
Unreal Tournament 2004 is the only game actually patched, in fact it
has been fixed before its pubblic release.
Unreal Tournament and Unreal Tournament 2003 are still vulnerable and
the patch is a mistery from 7 months.
I don't know if and how many other games are vulnerables.
#######################################################################
---
Luigi Auriemma
http://aluigi.altervista.org
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