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