Microsoft Security Bulletin MS01-055 (Version 2.0)

From: Microsoft Product Security (secnotif@MICROSOFT.COM)
Date: 11/14/01

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    Message-ID:  <2E08A46FF518C9418713A1B2C780684D103D3C@red-msg-20.redmond.corp.microsoft.com>
    Date:         Tue, 13 Nov 2001 21:02:11 -0800
    From: Microsoft Product Security <secnotif@MICROSOFT.COM>
    Subject:      Microsoft Security Bulletin MS01-055 (Version 2.0)
    To: MICROSOFT_SECURITY@ANNOUNCE.MICROSOFT.COM
    

    The following is a Security Bulletin from the Microsoft Product Security
    Notification Service.

    Please do not reply to this message, as it was sent from an unattended
    mailbox.
                        ********************************

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    - ----------------------------------------------------------------------
    Title: 13 November 2001 Cumulative Patch for IE
    Released: 08 November 2001
    Revised: 13 November 2001 (version 2.0)
    Software: Internet Explorer
    Impact: Exposure and altering of data in cookies
    Max Risk: Moderate
    Bulletin: MS01-055

    Microsoft encourages customers to review the Security Bulletin at:
    http://www.microsoft.com/technet/security/bulletin/MS01-055.asp.
    - ----------------------------------------------------------------------

    Reason for Revision:
    ====================
    On November 08, 2001, Microsoft released the original version of
    this bulletin. In it, we detailed a work-around procedure that
    customers could implement to protect themselves against a publicly
    disclosed vulnerability. On November 13, 2001, we released a patch
    that, when applied, eliminates all known vulnerabilities affecting
    IE 5.5 and IE 6. We therefore expanded the scope of the bulletin to
    discuss all of the vulnerabilities the patch addresses. Customers
    who disabled Active Scripting per the original version of this
    bulletin can re-enable it after installing this patch.

    Issue:
    ======
    In addition to eliminating all previously discussed vulnerabilities
    affecting IE 5.5 Service Pack 2 and IE 6, the patch also eliminates
    three newly discovered ones:

    The first two involve how IE handles cookies across domains.
    Although the underlying flaws are completely unrelated, the scope
    is exactly the same - in each case, a malicious user could
    potentially craft a URL that would allow them to gain unauthorized
    access to a user's cookies and potentially modify the values
    contained in them. Because some web sites store sensitive
    information in a user's cookies, this could allow personal
    information to be compromised. Both vulnerabilities could be
    exploited either by hosting specially crafted URL's on a web page
    or by sending them to the victim in an HTML email.

    The third vulnerability is a new variant of a vulnerability
    discussed in Microsoft Security Bulletin MS01-051 affecting how
    IE handles URLs that include dotless IP addresses. If a web site
    were specified using a dotless IP format (e.g.,
    http://031713501415 rather than http://207.46.131.13), and the
    request were malformed in a particular way, IE would not recognize
    that the site was an Internet site. Instead, it would treat the
    site as an intranet site, and open pages on the site in the
    Intranet Zone rather than the correct zone. This would allow the
    site to run with fewer security restrictions than appropriate.
    This vulnerability does not affect IE 6.

    Mitigating Factors:
    ====================
    Cookie Handling Vulnerabilities:

     - To exploit either vulnerability, the attacker would need to
       entice the user into visiting a particular web site or opening
       an HTML e-mail containing the malformed URL.

     - The Outlook Email Security Update (which is included as part
       of Outlook 2002 in Office XP) would protect the user against the
       mail-borne attack scenario.

     - Users who have set Outlook Express to use the "Restricted Sites"
       Zone are not affected by the mail-borne attack scenario, because
       the "Restricted Sites" zone sets Active Scripting to disabled.
       Note that this is the default setting for Outlook Express 6.0.
       Users of Outlook Express 6.0 should verify that Active Scripting
       is still disabled in the Restricted Sites Zone.
     
    Zone Spoofing Vulnerability:
     - The default settings in the Intranet Zone differ in only a few
       ways from those of the Internet Zone. The differences are
       enumerated in the FAQ in MS01-051, but none would allow
       destructive action to be taken.

    Patch Availability:
    ===================
     - A patch is available to fix this vulnerability. Please read the
       Security Bulletin at
       http://www.microsoft.com/technet/security/bulletin/ms01-055.asp
       for information on obtaining this patch.

    Acknowledgment:
    ===============
     - Marc Slemko for reporting one of the cookie handling issues.

    - ---------------------------------------------------------------------

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