VMware Workstation Shared Folders Directory Traversal Vulnerability

iDefense Security Advisory 04.27.07
http://labs.idefense.com/intelligence/vulnerabilities/
Apr 27, 2007

I. BACKGROUND

VMware Workstation is a software virtualization system which allows
multiple virtual computers to run on a single system. For more
information visit the following URL.

http://www.vmware.com/products/ws/

II. DESCRIPTION

Remote exploitation of a design error in the "Shared Folders" feature of
VMware Inc.'s VMware Workstation could allow an attacker to write
arbitrary content from a guest system to arbitrary locations on the
host system.

The "Shared Folders" feature of VMware Workstation allows folders on the
physical "host" system to be shared with virtual "guest" systems. Due to
a flaw in the code which validates that the filename is safe, an
attacker or malicious code within the guest system can read or write
files on the host system in the context of the user running
Workstation.

III. ANALYSIS

Exploitation allows an attacker to read or write arbitrary files on the
host system.

In order to exploit this vulnerability, the VMware system must have at
least one folder shared. Although the "Shared Folders" feature is
enabled by default, no folders are shared by default. If the 'Read
Only' option for a shared folder is set, the attacker will only be able
to read files from the host.

The documentation states that VMware Tools must be installed in order to
use the "Shared Folders" feature. While this is true of normal use of
the feature, VMware Tools is not required to exploit this
vulnerability. The vulnerable functionality is supplied by the
"Backdoor I/O Port" interface. Some details of the interface protocol
are publicly available. These details provide a starting point which
allow an attacker to reverse engineer enough of the protocol to
implement their own tool for performing these operations.

IV. DETECTION

iDefense confirmed this vulnerability to exist in VMware Workstation
5.5.3 build 34685 on a Windows XPSP2 host. Other versions may also be
affected.

V. WORKAROUND

Disabling the "Shared Folders" feature in VMware will prevent exposure
to this vulnerability.

VI. VENDOR RESPONSE

VMware Inc. has addressed this vulnerability by releasing new versions
of their software. More information is available in the release notes
provided by VMware Inc.

VII. CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CVE-2007-1744 to this issue. This is a candidate for inclusion in
the CVE list (http://cve.mitre.org/), which standardizes names for
security problems.

VIII. DISCLOSURE TIMELINE

03/20/2007  Initial vendor notification
03/20/2007  Initial vendor response
04/27/2007  Coordinated public disclosure

IX. CREDIT

This vulnerability was discovered by Greg MacManus of iDefense Labs.

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X. LEGAL NOTICES

Copyright © 2007 iDefense, Inc.

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Disclaimer: The information in the advisory is believed to be accurate
at the time of publishing based on currently available information. Use
of the information constitutes acceptance for use in an AS IS condition.
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