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Microsoft Outlook / Microsoft Exchange TNEF Decoding Remote Code Execution Vulnerability

Risk
High

Date Discovered
01-10-2006

Description
Microsoft Exchange Server and Outlook email clients are prone to a remote code execution vulnerability.

This vulnerability presents itself when the applications decode a message containing a specially crafted TNEF MIME attachment. Successful exploitation may result in arbitrary code execution facilitating a remote compromise.

An attack against Microsoft Exchange Server could lead to a SYSTEM level remote compromise, while attacks against Outlook would result in arbitrary code execution in the context of the current user.

AntiVirus Products
A heuristic detection will be available as of January 11, 2006 to detect possible exploits of this vulnerability. Symantec Antivirus products will detect files which contain code to exploit this vulnerability as Bloodhound.Exploit.57.

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 11, 2006.

Symantec Vulnerability Assessment
Symantec Vulnerability Assessment detects and reports this vulnerability. Click here for the advisory released January 11, 2006.

Platforms Affected
Microsoft BackOffice 4.5
Microsoft Excel 2002 SP3
Microsoft FrontPage 2002 SP3
Microsoft Office 2000 SP3
Microsoft Outlook 2002 SP3
Microsoft PowerPoint 2002 SP3
Microsoft Publisher 2002 SP3
Microsoft Windows 2000 Professional
Microsoft Windows 2000 Professional SP1
Microsoft Windows 2000 Professional SP2
Microsoft Windows 2000 Professional SP3
Microsoft Windows 98
Microsoft Windows 98SE
Microsoft Windows ME
Microsoft Windows NT 4.0
Microsoft Windows NT 4.0 SP1
Microsoft Windows NT 4.0 SP2
Microsoft Windows NT 4.0 SP3
Microsoft Windows NT 4.0 SP4
Microsoft Windows NT 4.0 SP5
Microsoft Windows NT 4.0 SP6
Microsoft Windows NT 4.0 SP6a
Microsoft Windows NT Workstation 4.0
Microsoft Windows NT Workstation 4.0 SP1
Microsoft Windows NT Workstation 4.0 SP2
Microsoft Windows NT Workstation 4.0 SP3
Microsoft Windows NT Workstation 4.0 SP4
Microsoft Windows NT Workstation 4.0 SP5
Microsoft Windows NT Workstation 4.0 SP6
Microsoft Windows NT Workstation 4.0 SP6a
Microsoft Windows XP Home
Microsoft Windows XP Home SP1
Microsoft Windows XP Professional
Microsoft Windows XP Professional SP1
Microsoft Word 2002 SP3

Components Affected
Microsoft Exchange Server 5.0 SP2
Microsoft Exchange Server 5.0 SP1
Microsoft Exchange Server 5.0
Microsoft Exchange Server 5.5 SP4
Microsoft Exchange Server 5.5 SP3
Microsoft Exchange Server 5.5 SP2
Microsoft Exchange Server 5.5 SP1
Microsoft Exchange Server 5.5
Microsoft Exchange Server 2000 SP3
Microsoft Office 2000 SP3

Recommendations
Block external access at the network boundary, unless service is required by external parties.
Deploy network access controls to permit access to the server for trusted or internal networks and computers only. This could include permitting remote access to the server through a VPN connection. Access controls should also be established at the network perimeter to explicitly deny access by all unauthorized computers and networks.

Run all client software as a non-privileged user with minimal access rights.
Running the affected Outlook client as a user with least privileges possible may help mitigate the impact of a successful attack.

Deploy network intrusion detection systems to monitor network traffic for malicious activity.
Deploy network intrusion detection systems to monitor network traffic for signs of anomalous or suspicious activity. Server logs should also be monitored on a regular basis for any signs of unusual activity, such as repeated crashes of services.

Run all server processes as non-privileged users with minimal access rights.
If possible, run the server as an unprivileged user with minimal access rights. This may limit the consequences of successful exploitation of this and other latent vulnerabilities.

Do not accept communications that originate from unknown or untrusted sources.
Users should avoid trusting incoming email messages of enticing or suspicious nature.

Implement multiple redundant layers of security.
Memory protection schemes such as non-executable stack/heap configurations and randomly mapped memory segments may complicate exploitation of memory corruption vulnerabilities.

Microsoft has released fixes for supported applications.


Microsoft Exchange Server 5.0 SP2:

Microsoft Upgrade Security Update for Exchange 5.0 Server (KB894689)
http://www.microsoft.com/downloads/details.aspx?familyid=0A8DF1C3-ABF9-4A21-9B49-81FA362B251F&displaylang=en

Microsoft Exchange Server 5.0 SP1:
Microsoft Exchange Server 5.0:
Microsoft Exchange Server 5.5 SP4:
Microsoft Upgrade Security Update for Exchange Server 5.5 Service Pack 4 (KB894689)
http://www.microsoft.com/downloads/details.aspx?FamilyId=EC6BD30E-12DE-4CA1-9432-D2E73AF62427

Microsoft Exchange Server 5.5 SP3:
Microsoft Exchange Server 5.5 SP2:
Microsoft Exchange Server 5.5 SP1:
Microsoft Exchange Server 5.5:
Microsoft Exchange Server 2000 SP3:
Microsoft Upgrade Security Update for Exchange 2000 Server (KB894689)
http://www.microsoft.com/downloads/details.aspx?familyid=372FF07F-C3CA-4301-8559-9B90344EDC02&displaylang=en

Microsoft Office 2000 SP3:
Microsoft Upgrade Security Update for Outlook 2000 (KB892842)
http://www.microsoft.com/downloads/details.aspx?familyid=64D0336D-F962-4AB1-A724-9F6BA2108CB9&displaylang=en
Microsoft Upgrade Security Update for Office 2000 Multilanguage Pack (KB892842)
http://www.microsoft.com/downloads/details.aspx?familyid=2C0FA7C7-91AA-49B4-9731-9E83E3E0823D&displaylang=en
Microsoft Upgrade Security Update for Office 2000 Multilanguage Pack (KB892842)
http://www.microsoft.com/downloads/details.aspx?familyid=2C0FA7C7-91AA-49B4-9731-9E83E3E0823D&displaylang=en

References
Source: Microsoft Security Bulletin MS06-003
URL: http://www.microsoft.com/technet/security/Bulletin/MS06-003.mspx

Credits
Discovered by John Heasman and Marc Litchfield of NGS Software.


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Disclaimer
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