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VMware Workstation Shared Folders Directory Traversal Vulnerability

04.27.07

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/

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.

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.

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.

WORKAROUND

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

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.

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.

DISCLOSURE TIMELINE

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

CREDIT

This vulnerability was discovered by Greg MacManus of iDefense Labs.

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LEGAL NOTICES

Copyright © 2007 Verisign, Inc.

Permission is granted for the redistribution of this alert electronically. It may not be edited in any way without the express written consent of iDefense. If you wish to reprint the whole or any part of this alert in any other medium other than electronically, please e-mail customer service for permission.

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. There are no warranties with regard to this information. Neither the author nor the publisher accepts any liability for any direct, indirect, or consequential loss or damage arising from use of, or reliance on, this information.