EEYE: Microsoft WordPerfect Document Converter Buffer Overflow

From: Marc Maiffret (marc_at_EEYE.COM)
Date: 09/03/03

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    Date:         Wed, 3 Sep 2003 12:21:49 -0700
    To: NTBUGTRAQ@LISTSERV.NTBUGTRAQ.COM
    
    

    Microsoft WordPerfect Document Converter Buffer Overflow

    Release Date:
    September 3, 2003

    Reported Date:
    May 6, 2003

    Severity:
    Medium (Code Execution with User Interaction)

    Systems Affected:
    Microsoft Office 97, 2000, XP
    Microsoft Word 98 (J)
    Microsoft FrontPage 2000, 2002
    Microsoft Publisher 2000, 2002
    Microsoft Works Suite 2001, 2002, 2003

    Description:

    The Microsoft Word "WordPerfect" document converter included in Microsoft
    Word has a buffer overflow bug. If the WordPerfect document converter is
    installed (by default it is in Office 2000) and a malicious .doc file is
    opened, there exists the ability for an attacker to execute arbitrary code.

    This buffer overflow bug can also happen within Internet Explorer, because
    Microsoft Word is executed automatically as a helper-application when a .doc
    file is received.

    This buffer overflow overwrites the return address in the stack area. We
    confirmed that arbitrary code can be executed by using this buffer overflow
    bug.

    Technical Description:

    While parsing a WordPerfect file, the WordPerfect converter copies data
    stored in the .doc file to a local buffer. If we modify some bytes of the
    .doc file, we can specify the data offset and data size. The WordPerfect
    converter doesn't properly check the size of the data contained in the .doc
    file, and tries to copy all of the data from the file to the local buffer
    allocated in the stack area. This results in a typical buffer overflow
    vulnerability in which we can set any value for EIP.

    The process for making the .doc file to confirm this buffer overflow is as
    follows:

    [Technical data may wrap in eMail, please visit our website.]

    1. Open Word and save an empty document as wordPerfect 5.0 file.
    2. Open the .doc file in a binary editor. You'll be able to confirm the
    following dump image:

     ADDRESS 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F
    0123456789ABCDEF
    ----------------------------------------------------------------------------

    --
     00000000  FF 57 50 43 6D 02 00 00 01 0A 00 00 00 00 00 00
    .WPCm...........
      ...
     00000130  00 00 00 00 CD 01 00 00 08 00 02 00 00 00 CD 01
    ................
      ...
     000001C0  61 75 74 68 6F 72 00 65 45 79 65 00 00 00 00 FB
    author.eEye.....
     000001D0  FF 05 00 32 00 00 00 00 00 01 01 6C 00 00 00 01
    ...2.......l....
     000001E0  02 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
    ................
     000001F0  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
    ................
    3. Modify 0x00 to 0x01 in offset 0x00000139.
    4. Modify 0x00 to the value more than 0x80 in offset 0x000001D8.
    5. Modify 0x00 to the value more than 0x01 in offset 0x000001E1 to
    0x000001FF.
    6. Append garbage data (e.g., a long string of A's) onto the end of this
    file.
    Protection:
    Retina Network Security Scanner has been updated to identify this
    vulnerability.
    Vendor Status:
    Microsoft was notified on May 6, 2003, and has released a patch for this
    vulnerability. The patch is available at:
    http://www.microsoft.com/technet/security/bulletin/MS03-036.asp
    Credit:
    Yuji "The Ninja" Ukai, eEye Digital Security
    Related Links:
    Retina Network Security Scanner - Free 15 Day Trial
    http://www.eeye.com/html/Products/Retina/index.html
    Greetings:
    Shanti, Yukkie, TEX, Sakuranamiki people, AD200X people
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