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HistoryMay 16, 2002 - 12:00 a.m.

Security Bulletin MS02-023: 15 May 2002 Cumulative Patch for Internet Explorer (Q321232)

2002-05-1600:00:00
vulners.com
20

Title: 15 May 2002 Cumulative Patch for Internet Explorer
(Q321232)
Date: 15 May 2002
Software: Internet Explorer
Impact: Six new vulnerabilities, the most serious of which could
allow code of attacker's choice to run.
Max Risk: Critical
Bulletin: MS02-023

Microsoft encourages customers to review the Security Bulletin at:
http://www.microsoft.com/technet/security/bulletin/MS02-023.asp.


Issue:

This is a cumulative patch that includes the functionality of all
previously released patches for IE 5.01, 5.5 and 6.0. In addition,
it eliminates the following six newly discovered vulnerabilities:

  • A cross-site scripting vulnerability in a Local HTML Resource.
    IE ships with several files that contain HTML on the local file
    system to provide functionality. One of these files contains a
    cross-site scripting vulnerability that could allow a script to
    execute as if it were run by the user herself, causing it to run
    in the local computer zone. An attacker could craft a web page
    with a URL that exploits this vulnerability and then either host
    that page on a web server or send it as HTML email. When the web
    page was viewed and the user clicked on the URL link, the
    attacker's script injected into the local resource, the
    attacker's script would run in the Local Computer zone, allowing
    it to run with fewer restrictions than it would otherwise have.

  • An information disclosure vulnerability related to the use of am
    HTML object provides that support for Cascading Style Sheets that
    could allow an attacker to read, but not add, delete or change,
    data on the local system. An attacker could craft a web page
    that exploits this vulnerability and then either host that page
    on a web server or send it as HTML email. When the page was
    viewed, the element would be invoked. Successfully exploiting this
    vulnerability, however, requires exact knowledge of the location
    of the intended file to be read on the user's system. Further,
    it requires that the intended file contain a single, particular
    ASCII character.

  • An information disclosure vulnerability related to the handling
    of script within cookies that could allow one site to read the
    cookies of another. An attacker could build a special cookie
    containing script and then construct a web page with a hyperlink
    that would deliver that cookie to the user's system and invoke
    it. He could then send that web page as mail or post it on a
    server. When the user clicked the hyperlink and the page invoked
    the script in the cookie, it could potentially read or alter the
    cookies of another site. Successfully exploiting this, however,
    would require that the attacker know the exact name of the
    cookie as stored on the file system to be read successfully.

  • A zone spoofing vulnerability that could allow a web page to be
    incorrectly reckoned to be in the Intranet zone or, in some very
    rare cases, in the Trusted Sites zone. An attacker could construct
    a web page that exploits this vulnerability and attempt to entice
    the user to visit the web page. If the attack were successful,
    the page would be run with fewer security restrictions than
    is appropriate.

  • Two variants of the "Content Disposition" vulnerability
    discussed in Microsoft Security Bulletin MS01-058 affecting how
    IE handles downloads when a downloadable file's
    Content-Disposition and Content-Type headers are
    intentionally malformed. In such a case, it is possible for
    IE to believe that a file is a type safe for automatic
    handling, when in fact it is executable content. An attacker
    could seek to exploit this vulnerability by constructing a
    specially malformed web page and posting a malformed executable
    file. He could then post the web page or mail it to the intended
    target. These two new variants differ from the original
    vulnerability in that they for a system to be vulnerable, it
    must have present an application present that, when it is
    erroneously passed the malformed content, chooses to hand it
    back to the operating system rather than immediately raise
    an error. A successful attack, therefore, would require that
    the attacker know that the intended victim has one of these
    applications present on their system.

Finally, it introduces a behavior change to the Restricted Sites
zone. Specifically, it disables frames in the Restricted Sites
zone. Since the Outlook Express 6.0, Outlook 98 and Outlook 200
with the Outlook Email Security Update and Outlook 2002 all read
email in the Restricted Sites zone by default, this enhancement
means that those products now effectively disable frames in HTML
email by default. This new behavior makes it impossible for an
HTML email to automatically open a new window or to launch the
download of an executable.

Mitigating Factors:

Cross-Site Scripting in Local HTML Resource:

  • A successful attack requires that a user first click on a
    hyperlink. There is no way to automate an attack using
    this vulnerability.

  • Outlook 98 and 2000 (after installing the Outlook Email
    Security Update), Outlook 2002, and Outlook Express 6 all
    open HTML mail in the Restricted Sites Zone. As a result,
    customers using these products would not be at risk from
    email-borne attacks.

  • Customers using Outlook 2002 SP1 who have enabled the
    "Read as Plain Text" feature would be immune from the HTML
    email attack. This is because this feature disables all
    HTML elements, including scripting, from mail when it
    is displayed.

  • Any limitations on the rights of the user's account
    would also limit the actions of the attacker's script.

  • Customers who exercise caution in what web sites they
    visit or who place unknown or untrusted sites in the
    Restricted Sites zone can potentially protect themselves
    from attempts to exploit this issue on the web.

Local Information Disclosure through HTML Object:

  • It can only be used to read information. It cannot add,
    change or delete any information.

  • The attacker would need to know the exact name and
    location on the system of any file they attempted to read.

  • Only files that contained a particular, individual ASCII
    character could be read. If this single character is not
    present, the attempt to read the file would fail.

  • Outlook 98 and 2000 (after installing the Outlook Email
    Security Update), Outlook 2002, and Outlook Express 6 all
    open HTML mail in the Restricted Sites Zone. As a result,
    customers using these products would not be at risk from
    email-borne attacks.

  • Customers using Outlook 2002 SP1 who have enabled the
    "Read as Plain Text" feature would be immune from the
    HTML email attack. This is because this feature disables
    all HTML elements, including scripting, from mail when it
    is displayed.

Script within Cookies Reading Cookies:

  • The specific information an attacker could access would
    depend on what information a site has chosen to store in
    its cookies. Best practices strongly recommend against
    storing sensitive information in cookies.

  • An attacker would have to entice a user to first click on
    a hyperlink to initiate an attempt to exploit this
    vulnerability. There is no way to automate an attack that
    exploits this vulnerability.

  • Mounting a successful attack requires that the attacker
    know the exact name of the target cookie. This
    vulnerability provides no means for an attacker to
    acquire that information.

  • Outlook 98 and 2000 (after installing the Outlook Email
    Security Update), Outlook 2002, and Outlook Express 6
    all open HTML mail in the Restricted Sites Zone. As a
    result, customers using these products would not be at
    risk from email-borne attacks.

  • Customers using Outlook 2002 SP1 who have enabled the
    "Read as Plain Text" feature would be immune from the
    HTML email attack. This is because this feature disables
    all HTML elements, including scripting, from mail when it
    is displayed.

Zone Spoofing through Malformed Web Page:

  • A successful attack would require NetBIOS connectivity
    between the user and the attacker's site. Any filtering
    of NetBIOS, such as that found by ISP's or at the firewall
    perimeter, would thwart attempts to exploit this
    vulnerability.

  • Any attempt to render a web site in the Trusted Sites zone
    would require very specific knowledge of custom configuration
    made by the user. This aspect of the vulnerability is not
    exploitable by default, nor does the vulnerability give the
    means to acquire the necessary information for that attack.

New Variants of the "Content Disposition" Vulnerability:

  • Any successful attempt to exploit this vulnerability requires
    that the attacker know that the intended target have specific
    versions of specific applications on their system. The
    vulnerability gives no means for an attacker to know what
    applications or versions are present on the system.

  • Any attempt to exploit the vulnerability requires that the
    attacker host a malicious executable on a server accessible
    to the intended victim. If the hosting server is
    unreachable for any reason, such as DNS blocking or the
    server being taken down, the attack would fail.

Risk Rating:

  • Internet systems: Critical
  • Intranet systems: Critical
  • Client systems: Critical

Patch Availability:

Acknowledgment:

  • Jani Laatikainen ([email protected]) for reporting one of the
    "Content-Disposition variants.
  • Yuu Arai of LAC SNS Team (http://www.lac.co.jp/security/) for
    reporting one of the "Content-Disposition variants.
  • Cistobal Bielza Lino and Juan Carlos G. Cuartango from
    Instituto Seguridad Internet (www.instisec.com) for reporting
    the Zone Spoofing through Malformed Web Page vulnerability.

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