[NT] WinPcap NPF.SYS bpf_filter_init Arbitrary Array Indexing Vulnerability

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WinPcap NPF.SYS bpf_filter_init Arbitrary Array Indexing Vulnerability
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SUMMARY

<http://www.winpcap.org/> WinPcap is "a software package that facilitates
real-time link-level network access for Windows-based operating systems. A
wide range of open-source projects, including Wireshark, use it". Local
exploitation of an invalid array indexing vulnerability in the NPF.SYS
device driver of WinPcap allows attackers to execute arbitrary code in
kernel context.

DETAILS

Vulnerable Systems:
* WinPcap version 4.0.1 included in Wireshark version 0.99.6a
* NPF.SYS version 4.0.0.901

Immune Systems:
* WinPcap version 4.0.2

The problem specifically exists within the bpf_filter_init function. In
several places throughout this function, values supplied from a potential
attacker are used as array indexes without proper bounds checking. By
making IOCTL requests with specially chosen values, attackers are able to
corrupt the stack, or pool memory, within the kernel.

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. However, this is not the default setting.

Normally, 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 exits, 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.

Vendor response:
The WinPcap Team has addressed this vulnerability by releasing version
4.0.2 of the WinPcap software. For more information, see the following
URL: <http://www.winpcap.org/misc/changelog.htm>

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

CVE Information:
<http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2007-5756>
CVE-2007-5756

Disclosure timeline:
10/30/2007 - Initial vendor notification
10/30/2007 - Initial vendor response
11/12/2007 - Coordinated public disclosure

ADDITIONAL INFORMATION

The information has been provided by
<mailto:idlabs-advisories@idefense.com> iDefense Labs Security Advisories.
The original article can be found at:
<http://labs.idefense.com/intelligence/vulnerabilities/display.php?id=625>

http://labs.idefense.com/intelligence/vulnerabilities/display.php?id=625

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