Epic Games Fortnite 4.2-CL-4072250 Insecure File Permissions

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Epic Games Fortnite 4.2-CL-4072250 Insecure File Permissions  
  
  
Vendor: Epic Games, Inc.  
Product web page: https://www.epicgames.com  
Affected version: 4.2-CL-4072250  
4.1-CL-4053532  
4.0-CL-4039451  
  
  
Summary: Fortnite is a co-op sandbox survival game developed by Epic  
Games and People Can Fly and published by Epic Games. The game was  
released as a paid-for early access title for Microsoft Windows, macOS,  
PlayStation 4 and Xbox One on July 25, 2017, with a full free-to-play  
release expected in 2018. The retail versions of the game were published  
by Gearbox Publishing, while online distribution of the PC versions is  
handled by Epic's launcher.  
  
Desc: Fortnite suffers from an elevation of privileges vulnerability which  
can be used by a simple authenticated user that can change the executable  
file with a binary of choice. The vulnerability exist due to the improper  
permissions, with the 'C' flag (Change) for 'Authenticated Users' group.  
  
Tested on: Microsoft Windows 10 Home  
  
  
Vulnerability discovered by Gjoko 'LiquidWorm' Krstic  
@zeroscience  
  
  
Advisory ID: ZSL-2018-5469  
Advisory URL: https://www.zeroscience.mk/en/vulnerabilities/ZSL-2018-5469.php  
  
  
10.04.2018  
  
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E:\Program Files\Epic Games\Fortnite\FortniteGame>dir /b Binaries\Win64\*.exe  
FortniteClient-Win64-Shipping.exe  
FortniteClient-Win64-Shipping_BE.exe  
FortniteClient-Win64-Shipping_EAC.exe  
FortniteLauncher.exe  
  
E:\Program Files\Epic Games\Fortnite\FortniteGame>cacls Binaries  
E:\Program Files\Epic Games\Fortnite\FortniteGame\Binaries BUILTIN\Administrators:F  
BUILTIN\Administrators:(OI)(CI)(IO)F  
NT AUTHORITY\SYSTEM:F  
NT AUTHORITY\SYSTEM:(OI)(CI)(IO)F  
NT AUTHORITY\Authenticated Users:C  
NT AUTHORITY\Authenticated Users:(OI)(CI)(IO)C  
BUILTIN\Users:R  
BUILTIN\Users:(OI)(CI)(IO)(special access:)  
GENERIC_READ  
GENERIC_EXECUTE  
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