WinPcap NPF.SYS Local Privilege Escalation Vulnerability

iDefense Security Advisory 07.09.07
http://labs.idefense.com/intelligence/vulnerabilities/
Jul 09, 2007

I. BACKGROUND

WinPcap is a software package that facilitates real-time link-level
network access for Windows-based operating systems. It is used by a
wide range of open-source projects including Wireshark. More
information is available at the project web site at the URL shown
below.

http://www.winpcap.org/

II. DESCRIPTION

Local exploitation of an input validation vulnerability within the
NPF.SYS device driver of WinPcap allows attackers to execute arbitrary
code in kernel context.

The vulnerability specifically exists due to insufficient input
validation when handling the Interrupt Request Packet (Irp) parameters
passed to IOCTL 9031 (BIOCGSTATS). By passing carefully chosen
parameters to this IOCTL, an attacker can overwrite arbitrary kernel
memory.

III. ANALYSIS

Exploitation allows attackers to execute arbitrary code in kernel
context.

The vulnerable device driver is loaded when WinPcap is initialized. This
driver can be set to load on start-up depending on a choice made at
installation time. This is not the default setting.

In a default installation, the device driver is not loaded until an
Administrator utilizes a WinPcap dependent application. Once they do,
it will become accessible to normal users as well. When a program using
this driver exists, it is not unloaded. Attackers will continue to have
access until the driver is manually unloaded.

If the option to allow normal user access was chosen at installation
time, attackers will always have access to this device driver.
Consequently, a local attacker without administrator privileges would
have access to sniff, as well as exploit this vulnerability.

IV. DETECTION

iDefense has confirmed the existence of this vulnerability in version
4.0 of WinPcap as included in Wireshark 0.99.5. The version of NPF.SYS
tested was 4.0.0.755. Older versions are suspected to be vulnerable.

V. WORKAROUND

iDefense is currently unaware of any effective workaround for this
issue.

VI. VENDOR RESPONSE

The WinPcap Team has addressed this vulnerability by releasing version
4.0.1 of the WinPcap software. For more information, see the following
URL.

http://www.winpcap.org/misc/changelog.htm

VII. CVE INFORMATION

A Mitre Corp. Common Vulnerabilities and Exposures (CVE) number has not
been assigned yet.

VIII. DISCLOSURE TIMELINE

05/16/2007  Initial vendor notification
05/16/2007  Initial vendor response
07/09/2007  Coordinated public disclosure

IX. CREDIT

This vulnerability was reported to iDefense by Mario Ballano from
48bits.com.

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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.
 There are no warranties with regard to this information. Neither the
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indirect, or consequential loss or damage arising from use of, or
reliance on, this information.