Alert: Microsoft Security Bulletin - MS02-047

From: Russ (Russ.Cooper@RC.ON.CA)
Date: 08/23/02


Date:         Thu, 22 Aug 2002 20:10:59 -0400
From: Russ <Russ.Cooper@RC.ON.CA>
To: NTBUGTRAQ@LISTSERV.NTBUGTRAQ.COM

http://www.microsoft.com/technet/security/bulletin/MS02-047.asp

Cumulative Patch for Internet Explorer (Q323759)

Originally posted: August 22, 2002

Summary

Who should read this bulletin: Customers using Microsoft® Internet Explorer

Impact of vulnerability: Six new vulnerabilities, the most serious of which could enable an attacker to execute commands on a user's system.

Maximum Severity Rating: Critical

Recommendation: Customers should install the patch immediately.

Affected Software:
- Microsoft Internet Explorer 5.01
- Microsoft Internet Explorer 5.5
- Microsoft Internet Explorer 6.0

Technical description:

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 text 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.

Vulnerability identifiers:

- Buffer Overrun in Gopher Protocol Handler: CAN-2002-0646
- Buffer Overrun in Legacy Text Formatting ActiveX Control: CAN-2002-0647
- XML File Reading via Redirect: CAN-2002-0648
- File Origin Spoofing: CAN-2002-0722
- Cross Domain Verification in Object Tag: CAN-2002-0723
- Variant of Cross-Site Scripting in Local HTML Resource: CAN-2002-0691

This email is sent to NTBugtraq automatically as a service to my subscribers. Since its programmatically created, and since its been a long time since anyone paid actual money for my programming skills, it may or may not look that good...;-]

I can only hope that the information it does contain can be read well enough to serve its purpose.

Cheers,
Russ - Surgeon General of TruSecure Corporation/NTBugtraq Editor



Relevant Pages

  • Re: Microsoft Security Bulletin MS03-040 - 828750
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  • Re: Microsoft Security Bulletin MS03-040 - 828750
    ... cross-posts fake Microsoft Security bulletins [which, by the way, ALSO have ... Cumulative Patch for Internet Explorer ... A vulnerability that occurs because Internet Explorer does not ... It could be possible for an attacker who exploited this ...
    (microsoft.public.security.virus)
  • Re: Microsoft Security Bulletin MS03-040 - 828750
    ... cross-posts fake Microsoft Security bulletins [which, by the way, ALSO have ... Cumulative Patch for Internet Explorer ... A vulnerability that occurs because Internet Explorer does not ... It could be possible for an attacker who exploited this ...
    (microsoft.public.win2000.security)
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    (Securiteam)
  • Re: Bulletin: MS03-040 Cumulative Patch for Internet Explorer (828750)
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