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Windows SMB version 2 vulnerability

Vulnerability Note VU#135940

Original Release Date: 2009-09-10 | Last Revised: 2009-09-16


Microsoft Windows Vista and Server 2008 do not correctly parse SMB version 2 messages.This vulnerability could allow an attacker to execute arbitrary code.


The Server Message Block version 2 (SMBv2) protocol is the successor to the original SMB protocol. SMBv2 is available in Windows Vista, Server 2008 and Windows 7 release candidates.

Windows Vista and Server 2008 fail to properly process fails to properly parse the headers for the Negotiate Protocol Request portion of an SMBv2 message.


An attacker may be able to execute arbitrary code or cause a vulnerable system to crash.


There is currently no solution to this problem. Until patches are available, users and administrators are encouraged to review the below workarounds.

Restrict access

Blocking access to ports 139/tcp and 445/tcp on vulnerable systems will mitigate this vulnerability. Administrators can configure mobile systems that use the Windows Firewall to open these ports only when the user is authenticated to a domain controller by using the firewall's "profile" feature.

Disable SMBv2

Disabling SMBv2 will mitigate this issue. The below steps to disable SMBv2 are provided in Microsoft Security Advisory 975497.

    1. Click Start, click Run, type Regedit in the Open box, and then click OK.
    2. Locate and then click the following registry subkey:
    3. HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services
    4. Click LanmanServer.
    5. Click Parameters.
    6. Right-click to add a new DWORD (32 bit) Value.
    7. Enter smb2 in the Name data field, and change the Value data field to 0.
    8. Exit.
    9. From a command prompt and with administrator privileges, type net stop server and then net start server.

    Vendor Information


    Microsoft Corporation Affected

    Updated:  September 10, 2009



    Vendor Statement

    We have not received a statement from the vendor.

    Vendor Information

    The vendor has not provided us with any further information regarding this vulnerability.

    CVSS Metrics

    Group Score Vector



    Thanks to Microsoft and Laurent Gaffié for information that was used in this report.

    This document was written by Ryan Giobbi.

    Other Information

    CVE IDs: CVE-2009-3103
    Severity Metric: 62.70
    Date Public: 2009-09-07
    Date First Published: 2009-09-10
    Date Last Updated: 2009-09-16 14:44 UTC
    Document Revision: 16

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