WelcomeEnterpriseSmall BusinessHome & Home OfficePartnersAbout Symantec

Microsoft ISA Server 2000 H.323 Filter Remote Buffer Overflow Vulnerability

Risk
High

Date Discovered
01-13-2004

Description
It has been reported that the H.323 filter used by Microsoft ISA Server 2000 is prone to a remote buffer overflow vulnerability. The condition presents itself due to insufficient boundary checks performed by the Microsoft Firewall Service on specially crafted H.323 traffic.

Successful exploitation of this vulnerability may allow a remote attacker to execute arbitrary code in the context of Microsoft Firewall Service running on ISA Server 2000. This may lead to complete control of the vulnerable system.

Symantec Enterprise Security Manager
Symantec Enterprise Security Manager™ posted an update to the OS Patch Policy that detects and reports systems that are not patched against this vulnerability. Click here for the advisory released January 14, 2004.

Symantec Vulnerability Assessment
Symantec Vulnerability Assessment detects and reports this vulnerability. Click here for the advisory released January 14, 2004.

Platforms Affected
Microsoft Windows 2000 Advanced Server
Microsoft Windows 2000 Advanced Server SP1
Microsoft Windows 2000 Advanced Server SP2
Microsoft Windows 2000 Datacenter Server SP1
Microsoft Windows 2000 Datacenter Server SP2
Microsoft Windows 2000 Server
Microsoft Windows 2000 Server SP1
Microsoft Windows 2000 Server SP2

Components Affected
Microsoft ISA Server 2000 SP1
Microsoft ISA Server 2000 FP1
Microsoft ISA Server 2000
Microsoft Small Business Server 2000
Microsoft Small Business Server 2003

Recommendations
Block external access at the network boundary, unless service is required by external parties.
Block TCP port 1720 at network perimeter or gateway. The H.323 filter listens on TCP port 1720 for incoming traffic, therefore blocking this port will protect against a remote attack.

Deploy network intrusion detection systems to monitor network traffic for malicious activity.
Use intrusion detection systems to monitor networks for anomalous activity and report attempted attacks.

Implement multiple redundant layers of security.
An attacker's ability to exploit this vulnerability to execute arbitrary code may be hindered through the use of various memory protection schemes. Where possible, implement the use of non-executable and randomly mapped memory segments.

Microsoft has released security advisory MS04-001 to address this issue. Users are strongly advised to obtain fixes.


Microsoft ISA Server 2000 SP1:

Microsoft Upgrade Vulnerability in H.323 Filter can cause Remote Code Execution (816458)
http://www.microsoft.com/downloads/details.aspx?FamilyId=CBE42990-4156-4E1D-9ACB-4CD449D9599B&displaylang=en

Microsoft ISA Server 2000 FP1:
Microsoft ISA Server 2000 :
Microsoft Small Business Server 2000 :
Microsoft Upgrade Vulnerability in H.323 Filter can cause Remote Code Execution (816458)
http://www.microsoft.com/downloads/details.aspx?FamilyId=CBE42990-4156-4E1D-9ACB-4CD449D9599B&displaylang=en

Microsoft Small Business Server 2003 :
Microsoft Upgrade Vulnerability in H.323 Filter can cause Remote Code Execution (816458)
http://www.microsoft.com/downloads/details.aspx?FamilyId=CBE42990-4156-4E1D-9ACB-4CD449D9599B&displaylang=en

References
Source: Microsoft Security Bulletin MS04-001
URL: http://www.microsoft.com/technet/treeview/default.asp?url=/technet/security/bulletin/MS04-001.asp

Credits
The disclosure of this issue has been credited to the University of Oulu Security Programming Group.


Copyright (c) 2004 by Symantec Corp.
Permission to redistribute this alert electronically is granted as long as it is not edited in any way unless authorized by Symantec Security Response. Reprinting the whole or part of this alert in any medium other than electronically requires permission from symsecurity@symantec.com.

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.

Symantec, Symantec products, Symantec Security Response, and SymSecurity are registered trademarks of Symantec Corp. and/or affiliated companies in the United States and other countries. All other registered and unregistered trademarks represented in this document are the sole property of their respective companies/owners.