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Title: Cumulative Patch for Internet Explorer (Q323759)
Date: 22 August 2002
Software: Internet Explorer
Impact: Six new vulnerabilities, the most serious of which
could enable an attacker to execute commands on a
user's system.
Max Risk: Critical
Bulletin: MS02-047

Microsoft encourages customers to review the Security Bulletin at:
http://www.microsoft.com/technet/security/bulletin/MS02-047.asp.

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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 buffer overrun vulnerability affecting the Gopher protocol
  handler. This vulnerability was originally discussed in
  Microsoft Security Bulletin MS02-027, which provided workaround
  instructions while the patch provided here was being completed.

• A buffer overrun vulnerability affecting an ActiveX control used
  to display specially formatted text. The control contains a buffer
  overrun vulnerability that could enable an attacker to run code
  on a user?s system in the context of the user.

• A vulnerability involving how Internet Explorer handles an HTML
  directive that displays XML data. By design, the directive
  should only allow XML data from the web site itself to be
  displayed. However, it does not correctly check for the case
  where a referenced XML data source is in fact redirected to a
  data source in a different domain. This flaw could enable an
  attacker?s web page to open an XML-based files residing a
  remote system within a browser window that the site could
  read, thereby enabling the attacker to read contents from
  websites that users had access to but the attacker was not
  able to navigate to.

• A vulnerability involving how Internet Explorer represents the
  origin of a file in the File Download Dialogue box. This flaw
  could enable an attacker to misrepresent the source of a file
  offered for download in an attempt to fool users into
  accepting a file download from an untrusted source believing
  it to be coming from a trusted source.

• A Cross Domain verification vulnerability that occurs because
  of improper domain checking in conjunction with the Object tag.
  As a result, the vulnerability could enable a malicious web
  site operator to access data across different domains, for
  example one in a web site?s domain and the other on the
  user?s local file system and then pass information from the
  latter to the former. This could enable the web site operator
  to read, but not change, any file on the user?s local computer
  that could be viewed n a browser window. In addition, this can
  also enable an attacker to invoke, but not pass parameters to,
  an executable on the local system, much like the
  "Local Executable Invocation via Object tag" vulnerability
  discussed in MS02-015.

• A newly reported variant of the "Cross-Site Scripting in Local
  HTML Resource" vulnerability originally discussed in
  Microsoft Security Bulletin MS02-023. Like the original
  vulnerability, this variant could enable an attacker to create
  a web page that, when opened, would run in the Local Computer
  zone, allowing it to run with fewer restrictions than it would
  in the Internet Zone.

In addition, the patch sets the Kill Bit on the MSN Chat ActiveX
control discussed in Microsoft Security Bulletin MS02-022 as well
as the TSAC ActiveX control discussed in Microsoft Security
Bulletin MS02-046. This has been done to ensure that vulnerable
controls cannot be introduced onto users? systems. Customers
who use the MSN Chat control should ensure that they have applied
the updated version of the control discussed in MS02-022 and
customers who use the TSAC control should ensure that they
have applied the updated version of the control discussed
in MS02-046 .

Mitigating Factors:

Buffer Overrun in Gopher Protocol Handler:

• The vulnerability would provide the attacker with user?s own
  privileges on the system. Customers who run with fewer than
  full privileges on the system would therefore be at lower risk.

Buffer Overrun in Legacy Text Formatting ActiveX Control:

• The vulnerable ActiveX control is not installed by default as
  part of a current version of IE. Upon learning of the
  vulnerability, Microsoft removed the download from its site
  to minimize the likelihood that users would have the control
  on their systems.

• The vulnerability would provide the attacker with the user?s
  own privileges on the system. Customers who run with fewer
  than full privileges on the system would therefore be at
  lower risk.

• Customers who use Outlook Express 6.0 or Outlook 2002
  (or Outlook 98 or 2000 in conjunction with the Outlook Email
  Security Update) would by default by protected against
  email-borne attacks via this vulnerability unless they
  specifically clicked a link within the email message.

XML File Reading via Redirect:

• The vulnerability only provides a capability to read
  XML-based files that they know the complete path to.

• The vulnerability could not be used to add, change or delete
  files.

• Customers who use Outlook Express 6.0 or Outlook 2002
  (or Outlook 98 or 2000 in conjunction with the Outlook Email
  Security Update) would by default by protected against
  email-borne attacks via this vulnerability.

File Origin spoofing:

• The vulnerability does not give an attacker the means to
  place or run executables directly on the system: user
  interaction is required in a successful attack.

Cross Domain Verification in Object Tag:

• The vulnerability would not enable the attacker to pass any
  parameters to an executable program. Microsoft is not aware
  of any programs installed by default in any version of
  Windows that, when called with no parameters, could be used
  to compromise the system.

• An attacker could only invoke a file on the victim?s local
  machine. The vulnerability could not be used to execute a
  program on a remote share or web site.

• The vulnerability would not provide any way for an attacker
  to put a program of his choice onto another user?s system.

• An attacker would need to know the name and location of any
  file on the system to successfully invoke it.

• The vulnerability could only be used to view or invoke files.
  It could not be used to create, delete, or modify them.

• The vulnerability would only allow an attacker to read files
  that can be rendered in a browser window, such as image files,
  HTML files and ext files. Other file types, such as binary
  files, executable files, Word documents, and so forth, could
  not be read.

• 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.

Variant of Cross-Site Scripting in Local HTML Resource:

• 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
  automated email-borne attacks. However, these customers can
  still be attacked if they choose to click on a hyperlink in a
  malicious HTML email.

• 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.

Aggregate Severity of all issues included in this patch
(including issues addressed in previously released patches):

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

Patch Availability:

• A patch is available to fix this vulnerability. Please read the
  Security Bulletin at
  http://www.microsoft.com/technet/security/bulletin/ms02-047.asp
  for information on obtaining this patch.

Acknowledgment:

• GreyMagic Software (http://sec.greymagic.com/news/) for
  reporting the XML File Reading via Redirect vulnerability.

• Mark Litchfield of Next Generation Security Software Ltd.
  (http://www.nextgenss.com/) for reporting the Buffer Overrun
  in Legacy Text Formatting ActiveX Control vulnerability.

• Jouko Pynnonen of Oy Online Solutions Ltd for reporting
  the File Origin Spoofing vulnerability.

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