ShaprLynx v9.2.3 Insecure File Permissions Vendor: Lynx Software Pty Ltd. Product web page: https://www.sharplynx.com Affected version: 9.02.0003 Summary: Back Office Software for Sharp POS Terminals. Catering for the needs of retail and hospitality businesses, SharpLynx has been developed as a modular software solution with options from simple program management and sales analysis through to multi-location stock control. Desc: SharpLynx 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 7 Professional SP1 (EN) Vulnerability discovered by Gjoko 'LiquidWorm' Krstic @zeroscience Advisory ID: ZSL-2018-5456 Advisory URL: https://www.zeroscience.mk/en/vulnerabilities/ZSL-2018-5456.php 27.03.2018 -- C:\>cacls "Lynx Software" C:\Lynx Software BUILTIN\Administrators:(ID)F BUILTIN\Administrators:(OI)(CI)(IO)(ID)F NT AUTHORITY\SYSTEM:(ID)F NT AUTHORITY\SYSTEM:(OI)(CI)(IO)(ID)F BUILTIN\Users:(OI)(CI)(ID)R NT AUTHORITY\Authenticated Users:(ID)C NT AUTHORITY\Authenticated Users:(OI)(CI)(IO)(ID)C C:\Lynx Software\SharpLynx v9>dir *.exe Volume in drive C has no label. Volume Serial Number is 54D3-A5E6 Directory of C:\Lynx Software\SharpLynx v9 02/22/2018 02:23 PM 527,840 SL.exe 02/22/2018 02:23 PM 6,747,104 SLE.exe 02/22/2018 02:23 PM 6,747,104 SLED.exe 02/22/2018 02:23 PM 6,747,104 SLER.exe 02/22/2018 02:23 PM 4,932,064 SLU.exe 02/22/2018 02:23 PM 4,932,064 SLUR.exe 07/15/2016 05:58 PM 7,590,288 TeamViewerQS_en.exe 7 File(s) 38,223,568 bytes 0 Dir(s) 2,677,899,264 bytes free C:\Lynx Software\SharpLynx v9>cacls *.exe C:\Lynx Software\SharpLynx v9\SL.exe BUILTIN\Administrators:(ID)F NT AUTHORITY\SYSTEM:(ID)F BUILTIN\Users:(ID)R NT AUTHORITY\Authenticated Users:(ID)C C:\Lynx Software\SharpLynx v9\SLE.exe BUILTIN\Administrators:(ID)F NT AUTHORITY\SYSTEM:(ID)F BUILTIN\Users:(ID)R NT AUTHORITY\Authenticated Users:(ID)C C:\Lynx Software\SharpLynx v9\SLED.exe BUILTIN\Administrators:(ID)F NT AUTHORITY\SYSTEM:(ID)F BUILTIN\Users:(ID)R NT AUTHORITY\Authenticated Users:(ID)C C:\Lynx Software\SharpLynx v9\SLER.exe BUILTIN\Administrators:(ID)F NT AUTHORITY\SYSTEM:(ID)F BUILTIN\Users:(ID)R NT AUTHORITY\Authenticated Users:(ID)C C:\Lynx Software\SharpLynx v9\SLU.exe BUILTIN\Administrators:(ID)F NT AUTHORITY\SYSTEM:(ID)F BUILTIN\Users:(ID)R NT AUTHORITY\Authenticated Users:(ID)C C:\Lynx Software\SharpLynx v9\SLUR.exe BUILTIN\Administrators:(ID)F NT AUTHORITY\SYSTEM:(ID)F BUILTIN\Users:(ID)R NT AUTHORITY\Authenticated Users:(ID)C C:\Lynx Software\SharpLynx v9\TeamViewerQS_en.exe BUILTIN\Administrators:(ID)F NT AUTHORITY\SYSTEM:(ID)F BUILTIN\Users:(ID)R NT AUTHORITY\Authenticated Use rs:(ID)C C:\Lynx Software\SharpLynx v9>icacls SLE.exe SLE.exe BUILTIN\Administrators:(I)(F) NT AUTHORITY\SYSTEM:(I)(F) BUILTIN\Users:(I)(RX) NT AUTHORITY\Authenticated Users:(I)(M) Successfully processed 1 files; Failed processing 0 files