[NT] Windows SMB Client Transaction Response Handling Technical Details (MS05-011)

From: SecuriTeam (support_at_securiteam.com)
Date: 02/13/05

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    To: list@securiteam.com
    Date: 13 Feb 2005 11:06:06 +0200

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      Windows SMB Client Transaction Response Handling Technical Details


    eEye Digital Security has discovered a vulnerability in Windows SMB
    client's handling of SMB responses. An attacker who can cause an affected
    system to connect to the SMB service on a malicious host may exploit this
    vulnerability in order to execute code on the victim's machine.


    Vulnerable Systems:
     * Windows 2000
     * Windows XP
     * Windows Server 2003
    For detailed information regarding vulnerable systems refer to the
    advisory linked in the 'Vendor Status' section below.

    The driver MRXSMB.SYS is responsible for performing SMB client operations
    and processing the responses returned by an SMB server service. A number
    of important Windows File Sharing operations, and all
    RPC-over-named-pipes, use the SMB commands Trans (25h) and Trans2 (32h). A
    malicious SMB server can respond with specially crafted Transaction
    response data that will cause an overflow wherever the data is handled,
    either in MRXSMB.SYS or in client code to which it provides data. One
    example would be if the file name and short file name length fields in a
    Trans2 FIND_FIRST2 response packet can be supplied with inappropriately
    large values in order to cause an excessive memcpy to occur when the data
    is handled. In the case of these examples an attacker could leverage
    file:// links, that when clicked by a remote user, would lead to code

    Vendor Status:
    Advisory release date: February 8, 2005
    Date Reported to vendor: August 2, 2004

    Microsoft has released an advisory and patches for this vulnerability. The
    patch is available at:
    Vulnerability in Server Message Block Could Allow Remote Code Execution


    The information has been provided by <mailto:mmaiffret@eeye.com> Marc
    The original article can be found at:


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