Title: ArcServe UDP - Unquoted Service Path Privilege Escalation
CWE Class: CWE-427: Uncontrolled Search Path Element
Date: 04/09/2016
Vendor: ArcServe
Product: ArcServe UDP Standard Edition for Windows, TRIAL
Type: Backup Software
Version: 6.0.3792 Update 2 Build 516
Download URL: http://arcserve.com/free-backup-software-trial/
Tested on: Windows 7x86 EN
Release Mode: coordinated release


- 1. Product Description: -
A comprehensive solution that empowers even a one-person IT department to protect virtual and physical environments with a high degree of simplicity:
Design and manage your entire data protection strategy with a unified management console
Scale your data backup coverage as your organization grows with the push of a button

- 2. Vulnerability Details: -
ArcServe UDP for Windows installs various services. 
One of them is the "Arcserve UDP Update Service (CAARCUpdateSvc)" running as SYSTEM. 
This particular service has an insecurely quoted path. 
Other services where correctly quoted.
An attacker with write permissions on the root-drive or directory in the search path
could place a malicious binary and elevate privileges.

- 3. PoC Details: -
There are various ways to audit for this type of vulnerability. 
This proof-of-concept demonstrates both an automated and manual way.

Step 1: Identify the issue
Automatic: use the windows-privesc-check toolkit to audit the local system. 
Manual: run 'sc qc CAARCUpdateSvc' and confirm it has an unquoted service path.

Output: C:\Program Files\Arcserve\Unified Data Protection\Update Manager\ARCUpdate.exe
This should be: "C:\Program Files\Arcserve\Unified Data Protection\Update Manager\ARCUpdate.exe"

Step 2: Assess if exploitation is possible
To exploit this issue assess the permissions of each folder in the path using space as a token.

If any of the directories is writable for a non-administrative user, try to exploit the issue.

Step 3 Exploitation: 
Place a binary with the correct name in the vulnerable directory.
Reboot the system and validate your payload is executed with SYSTEM privileges

- 4. Vendor Mitigation: -
Create an update for the product which add quotes to the path.

While the update is being developed customers could apply a manual fix:
Open regedit, browse to HKLM\SYSTEM\CurrentControlSet\services 
Add quotes to the ImagePath value of the relevant service.

- 5. End-user Mitigation: -
A patch has been released by Arcserve.
All customer should upgrade to the latest version as described in the release notes:
http://documentation.arcserve.com/Arcserve-UDP/Available/V6/ENU/Bookshelf_Files/HTML/Update3/Default.htm#Update3/upd3_Issues_Fixed.htm%3FTocPath%3D_____6

- 6. Author: -
sh4d0wman / Herman Groeneveld
herman_worldwide AT hotmail. com

- 7. Timeline: -
* 01/06/2016: Vulnerability discovery
* 18/06/2016: Request sent to  info@arcserve.com for a security point-of-contact 
* 21/06/2016: Received contact but no secure channel. Requested confirmation to send PoC over unsecure channel
* 22/06/2016: vendor supplied PGP key, vulnerability PoC sent
* 09/07/2016: Received information: 2 out of 3 issues have fixes pending. 
Vendor requests additional mitigation techniques for the third issue. 
* 13/07/2016: Sent vendor various mitigation solutions and their limitations.
* 13/08/2016: Vendor informs release is pending for all discovered issues.
* 15/08/2016: Vendor requests text for release bulletin.
* 19/08/2016: A fix has been released.