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AUSCERT External Security Bulletin Redistribution
ESB-2009.1527
Vulnerability in SMB Could Allow Denial of Service
14 November 2009
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AusCERT Security Bulletin Summary
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Product: SMB
Publisher: Microsoft
Operating System: Windows 7
Windows Server 2008
Impact/Access: Denial of Service -- Remote with User Interaction
Resolution: Mitigation
CVE Names: CVE-2009-3676
Reference: http://www.auscert.org.au/11954
Original Bulletin:
http://www.microsoft.com/technet/security/advisory/977544.mspx
Comment: Please note it is Server 2008 R2 that is affected, along with
Windows 7.
Exploit code for this vulnerability has been made public.
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Microsoft Security Advisory (977544)
Vulnerability in SMB Could Allow Denial of Service
Published: November 13, 2009
Version: 1.0
General Information
Executive Summary
Microsoft is investigating new public reports of a possible denial of
service vulnerability in the Server Message Block (SMB) protocol. This
vulnerability cannot be used to take control of or install malicious
software on a users system. However, Microsoft is aware that detailed
exploit code has been published for the vulnerability. Microsoft is not
currently aware of active attacks that use this exploit code or of
customer impact at this time. Microsoft is actively monitoring this
situation to keep customers informed and to provide customer guidance as
necessary.
Affected Software
Windows 7 for 32-bit Systems
Windows 7 for x64-based Systems
Windows Server 2008 R2 for x64-based Systems*
Windows Server 2008 R2 for Itanium-based Systems
*Server Core installation affected.
Workarounds
Block TCP ports 139 and 445 at the firewall
These ports are used to initiate a connection with the affected component.
Blocking TCP ports 139 and 445 at the firewall will help protect systems
that are behind that firewall from attempts to exploit this vulnerability.
Microsoft recommends that you block all SMB communications to and from the
Internet to help prevent attacks. For more information about ports, see
TCP and UDP Port Assignments.
Impact of Workaround: Several Windows services use the affected ports.
Blocking connectivity to the ports may cause various applications or
services to not function. Some of the applications or services that could
be impacted are listed below:
Applications that use SMB (CIFS)
Applications that use mailslots or named pipes (RPC over SMB)
Server (File and Print Sharing)
Group Policy
Net Logon
Distributed File System (DFS)
Terminal Server Licensing
Print Spooler
Computer Browser
Remote Procedure Call Locator
Fax Service
Indexing Service
Performance Logs and Alerts
Systems Management Server
License Logging Service
How to undo the workaround. Unblock TCP ports 139 and 445 at the firewall.
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The University of Queensland
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Qld 4072
Internet Email: auscert@auscert.org.au
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