Microsoft Windows Kernel Remote Code Execution Vulnerability

Date Published : 08 August 2006

Date Last Revised : 08 August 2006

Overview : A remote code execution vulnerability exists in the Microsoft Windows Kernel.

This vulnerability has been classified as "High Risk." Computer users should take appropriate action to patch vulnerable systems.

Description : The vulnerability is caused in that Windows 2000 Winlogon does not prohibit the use of an invalid path. If a specially crafted DLL is placed in the user directory, it is possible for WinLogon to execute the code of the DLL resulting in an elevation of the user’s privileges.

The vulnerability is also caused by improper exception handling in memory resident applications.

Winlogon is the process that manages security-related user interactions in Windows. It handles logon and logoff requests, locking or unlocking the machine, changing the password, and other requests.

DLLs provide a way to modularize applications so that their functionality can be updated and reused more easily. DLLs also help reduce memory overhead when several applications use the same functionality at the same time, because although each application receives its own copy of the DLL data, the applications share the DLL code.

An attacker who successfully exploited this vulnerability could take complete control of an affected system.

Impact : To exploit this vulnerability, an attacker would first have to log on to the system. An attacker could then place a specially crafted DLL within their UserProfile directory and then restart the computer. After the restart and subsequent re-logon by the attacker, the DLL would execute code that could exploit the vulnerability and allow the attacker to gain complete control over the affected system.

Another way to exploit this vulnerability through a Web-based attack scenario, an attacker would have to host a Web site that contains a Web page that is used to attempt to exploit this vulnerability. An attacker would have no way to force users to visit a specially crafted Web site. Instead, an attacker would have to persuade them to visit the Web site, typically by getting them to click a link that takes them to the attacker's site. It could also be possible to display specially crafted Web content by using banner advertisements or by using other methods to deliver Web content to affected systems.

An attack that is successfully exploited would enable an attacker to install malicious code (worm, virus, Trojan horse), read confidential data, or take control over the target system.

Platforms Affected : Please review the Microsoft Security Bulletin MS06051 for a complete list of affected platforms: http://www.microsoft.com/technet/security/bulletin/MS06051.mspx

ZoneAlarm Products That Provide Protection : To ensure the most comprehensive protection, computer users should employ ZoneAlarm Security Suite, or ZoneAlarm Pro. Zone Labs products are not vulnerable to this attack. All Zone Labs security products, including ZoneAlarm, protect the user's system from unauthorized access and intrusions, and alert the user when malicious code attempts to access the network.

Recommended Actions :

ZoneAlarm Family

ZoneAlarm Pro and ZoneAlarm Security Suite protect your system against this vulnerability through "Internet Zone Security" and "Trusted Zone Security". It is recommended that you ensure the following:

• Internet Zone Security is set to High.
• Trusted Zone Security is set to Medium.
• Only trusted hosts are in the 'Trusted' Zone.

Check Point Integrity

Check Point Integrity protects your system against this vulnerability through the following available services:

Classic Firewall Rules

It is recommended that you ensure:

• Only trusted hosts are in the 'Trusted' Zone.

SmartDefense Program Advisor

SmartDefense Program Advisor automatically blocks malware. It is recommended that you ensure the following:

• Internet Zone Security is set to High.
• Trusted Zone Security is set to Medium.

For more information about activating SmartDefense Program Advisor, please refer to CPSA200510 .

Advanced Cooperative Enforcement

• Use Advanced Cooperative Enforcement to enforce policy upon remote endpoints.

Related Resources :

Install Microsoft patches to remove this vulnerability from the Windows Operating System and other software components: http://windowsupdate.microsoft.com

Review Microsoft Security Bulletin MS06051: http://www.microsoft.com/technet/security/Bulletin/MS06051.mspx

Disclaimer : The information in this 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.

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