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 -- 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