Title: Malformed Word Document Could Enable Macro to
Run Automatically
Date: 21 June 2001
Software: Word
Impact: Run macro without warning
Bulletin: MS01-034

Microsoft encourages customers to review the Security Bulletin at:
http://www.microsoft.com/technet/security/bulletin/MS01-034.asp.

Issue:

Word, like other members of the Office product family, provides a
security mechanism that requires the user's approval to run macros.
By
design, any time a document is opened Word scans it for macros. If
any
are found, they are handled in accordance with user's selected
security
settings. By default in Word 2000 and 2002, only macros that are
signed
by a trusted party are enabled; all others are disabled. In Word 97,
if
the document contains macros, the user is prompted regarding whether
to
enable them or disable them.

A vulnerability results because it is possible to modify a Word
document in such a way as to prevent the security scanner from
recognizing an embedded macro while still allowing it to execute.
Exploiting the vulnerability would enable an attacker to cause a
macro
to run automatically when such a document was opened. Such a macro
would be able to take any action that the user herself could take.
This
could include disabling the user's Word security settings so that
subsequently-opened Word documents would no longer be checked for
macros.

Mitigating Factors:

• The vulnerability only affects Word. Other Office products
  are not affected.
• Customers using the Outlook E-mail Security Update
  (which is included as part of Word 2002) will be protected
  from any worm viruses contained in Word documents.

Patch Availability:

• A patch is available to fix this vulnerability. Please read the
  Security Bulletin
  http://www.microsoft.com/technet/security/bulletin/ms01-034.asp
  for information on obtaining this patch.

Acknowledgment:

• Steven McLeod ([email protected])

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