Public Vulnerability Reports

VMware Tools HGFS Local Privilege Escalation Vulnerability

04.06.08

BACKGROUND

VMware is a software virtualization system which allows multiple virtual computers to run on a single system. VMware Tools provides drivers and utilities to enhance and optimize the experience within a guest operating system running under VMware. For more information visit the vendor's site at the following URL.

http://www.vmware.com/

DESCRIPTION

Local exploitation of an input validation vulnerability within VMware's Hgfs.sys driver could allow an unprivileged attacker to execute arbitrary code within the kernel of a Windows guest operating system.

When a VMware guest operating system has the VMware Tools package installed, the hgfs.sys driver is loaded on the machine. This driver allows any user to open the device "\.hgfs" and issue IOCTLs with a buffering mode of METHOD_NEITHER. This allows untrusted user mode code to pass kernel addresses as arguments to the driver.

With specially constructed input, a malicious user can use functionality within the driver to patch kernel addresses and execute arbitrary code in kernel mode.

ANALYSIS

Exploitation of this vulnerability allows an unprivileged local user to patch and execute arbitrary code within the kernel of a Windows guest operating system. In order to exploit the vulnerability, an attacker needs to be able to login to the target VMware guest virtual machine and execute a specially crafted executable.

DETECTION

iDefense confirmed the existence of this vulnerability in hgfs.sys as included with VMware Workstation 5.5.4. Other versions are suspected vulnerable as well.

WORKAROUND

Removing VMware Tools from affected guest systems will prevent exploitation of this issue. However, doing so will also reduce performance and affect the usability of that virtual machine.

VENDOR RESPONSE

VMware has addressed this vulnerability by releasing new versions of their affected products. In order to address affected guest operating systems, VMware Tools must be upgraded within the guest. For more information, consult VMware's advisory at the following URL.

http://www.vmware.com/security/advisories/VMSA-2008-0009.html

CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the name CVE-2007-5671 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

09/19/2007 Initial vendor notification
09/19/2007 Initial vendor response
06/04/2008 Coordinated public disclosure

CREDIT

This vulnerability was reported to iDefense by Stephen Fewer of Harmony Security.

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LEGAL NOTICES

Copyright © 2008 Verisign, Inc.

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