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ACROS Security Problem Report #2010-04-12-2

ASPR #2010-04-12-2: Local Binary Planting in VMware Tools for Windows

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
[email protected].

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: [email protected]
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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