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PUBLIC

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ACROS Security Problem Report #2010-04-12-2
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ASPR #2010-04-12-2: Local Binary Planting in VMware Tools for Windows
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Document ID:     ASPR #2010-04-12-2-PUB
Vendor:          VMware, Inc. (http://www.vmware.com)
Target:          VMware Tools for Windows 
Impact:          Local execution of arbitrary code on a virtual Windows
                 machine
Severity:        High
Status:          Official patch available, workarounds available
Discovered by:   Mitja Kolsek of ACROS Security

Current version 
   http://www.acrossecurity.com/aspr/ASPR-2010-04-12-2-PUB.txt


Summary
=======

A "binary planting" vulnerability in VMware Tools for Windows allows a 
local non-administrative attacker, under certain circumstances, to execute 
a malicious executable on virtual Windows machines in the context of 
logged- on users. 


Product Coverage
================

- VMware Tools for Windows build 91707
- VMware Tools for Windows version 7.8.4 build 126130
 
Note:  We only tested the above versions; other versions may also be 
affected. 


Analysis 
========

There is a code execution vulnerability in VMware Tools for Windows that 
allows a local attacker (being able to log on locally to the virtual 
machine) to plant a malicious executable with a specific name on the local 
drive and wait for this executable to get launched when another user logs 
on to the virtual machine.

While this scenario is usually blocked on default VMware Tools' 
installations on Windows XP, Windows Vista and Windows 7 due to the 
default file system ACLs, a non-administrative local attacker can launch 
the attack against virtual machines where VMware Tools were installed on 
non-default locations, e.g., on a non-system drive. Additionally, the 
attack is always possible on pre- Windows XP systems such as Windows 2000.

Additional details are available to interested corporate and government 
customers under NDA, as public disclosure would reveal too many details on 
the vulnerability and unduly accelerate malicious exploitation.


Mitigating Factors 
==================

- The attacker must be able to log on to the machine, or exploit another 
vulnerability on the machine to place the malicious executable on a local 
drive. Note that Windows Terminal Server allows multiple users to log on 
locally from remote and effectively act as local users. Additionally, the 
default configuration of Windows domain machines allows any domain user to 
log on locally to any domain computer (except the domain controller), 
which can be especially attacker-friendly in conjunction with remotely-
accessible desktops via VMware View.

- VMware Tools installations on Windows XP, Windows Vista and Windows 7 
are unaffected as long as (1) they're installed on the default location on 
system drive (usually C:\Program Files\VMware) and (2) the default file 
system ACLs haven't been modified.


Solution 
========

VMware has issued a security bulletin [1] and published remediated 
versions of VMware Workstation, Player, ACE, Server and Fusion, and 
patches for ESX and ESXi that fix this issue.

Warning: It is not enough to install the new version or the patch; it is 
also necessary to upgrade VMware Tools in each affected virtual machine. 
On VMware Workstation, Player, ACE, Server and Fusion, the user will be 
automatically prompted to upgrade, while there will be no such prompt on 
ESX and ESXi. The upgrade of VMware Tools requires a subsequent reboot of 
the virtual machine.


Workaround 
==========

Workarounds are available to interested corporate and government customers 
under NDA, as public disclosure would reveal too many details on the 
vulnerability and unduly accelerate malicious exploitation.


Related Services
================

ACROS is offering professional consulting on this issue to interested 
corporate and government customers. Typical questions we can help you 
answer are:

1) To what extent is your organization affected by this issue?

2) Have you adequately applied the remedies to remove the vulnerability?

3) Are there other workarounds that you could implement to fix this issue 
   more efficiently and/or inexpensively?

4) Are your systems or applications vulnerable to other similar issues?


Interested parties are encouraged to ask for more information at 
security@acrossecurity.com.
 

References
==========

[1] VMware Security Advisory VMSA-2010-0007 
    http://www.vmware.com/security/advisories/VMSA-2010-0007.html


Acknowledgments
===============

We would like to acknowledge VMware for professional handling of the 
identified vulnerability.


Contact
=======

ACROS d.o.o.
Makedonska ulica 113
SI - 2000 Maribor

e-mail: security@acrossecurity.com
web:    http://www.acrossecurity.com
phone:  +386 2 3000 280
fax:    +386 2 3000 282

ACROS Security PGP Key
   http://www.acrossecurity.com/pgpkey.asc
   [Fingerprint: FE9E 0CFB CE41 36B0 4720 C4F1 38A3 F7DD]

ACROS Security Advisories
   http://www.acrossecurity.com/advisories.htm

ACROS Security Papers
   http://www.acrossecurity.com/papers.htm

ASPR Notification and Publishing Policy
   http://www.acrossecurity.com/asprNotificationAndPublishingPolicy.htm


Disclaimer
==========

The content of this report is purely informational and meant only for the 
purpose of education and protection. ACROS d.o.o. shall in no event be 
liable for any damage whatsoever, direct or implied, arising from use or 
spread of this information. All identifiers (hostnames, IP addresses, 
company names, individual names etc.) used in examples and demonstrations 
are used only for explanatory purposes and have no connection with any 
real host, company or individual. In no event should it be assumed that 
use of these names means specific hosts, companies or individuals are 
vulnerable to any attacks nor does it mean that they consent to being used 
in any vulnerability tests. The use of information in this report is 
entirely at user's risk.


Revision History
================

April 12, 2010: Initial release


Copyright
=========

(c) 2010 ACROS d.o.o. Forwarding and publishing of this document is
permitted providing the content between "[BEGIN-ACROS-REPORT]" and
"[END-ACROS-REPORT]" marks remains unchanged.

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