Published:
13 December 2001
Protect yourself against future threats.
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AUSCERT External Security Bulletin Redistribution
ESB-2001.534 -- Microsoft Security Bulletin MS01-058
Cumulative Patch for IE
14 December 2001
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AusCERT Security Bulletin Summary
---------------------------------
Product: Internet Explorer 5.5
Internet Explorer 6
Vendor: Microsoft
Impact: Execute Arbitrary Code/Commands
Access Required: Remote
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Title: 13 December 2001 Cumulative Patch for IE
Date: 13 December 2001
Software: Internet Explorer
Impact: Run Code of an Attacker's Choice
Max Risk: Critical
Bulletin: MS01-058
Microsoft encourages customers to review the Security Bulletin at:
http://www.microsoft.com/technet/security/bulletin/MS01-058.asp.
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Issue:
======
This is a cumulative patch that, when installed, eliminates all
previously discussed security vulnerabilities affecting IE 5.5 and
IE 6. In addition, it eliminates three newly discovered
vulnerabilities.
- The first vulnerability involves a flaw in the handling of the
Content-Disposition and Content-Type header fields in an HTML.
stream. These fields, the hosting URL, and the hosted file data
determine how a file is handled upon download in Internet
Explorer. A security vulnerability exists because, if an
attacker altered the HTML header information in a certain way,
it could be possible to make IE believe that an executable file
was actually a different type of file -- one that it is
appropriate to simply open without asking the user for
confirmation. This could enable the attacker to create a web
page or HTML mail that, when opened, would automatically run an
executable on the user's system. This vulnerability affects
IE 6.0 only. It does not affect IE 5.5.
- The second vulnerability is a newly discovered variant of the
"Frame Domain Verification" vulnerability discussed in Microsoft
Security Bulletin MS01-015. The vulnerability could enable a
malicious web site operator to open two browser windows, one in
the web site's domain and the other on the user's local file
system, and to 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 opened in a
browser window. This vulnerabilty affects both IE 5.5 and 6.0.
- The third vulnerability involves a flaw related to the display
of file names in the File Download dialogue box. When a file
download is initiated, a dialogue provides the name of the file.
However, in some cases, it would be possible for an attacker to
misrepresent the name of the file in the dialogue. This could be
invoked from a web page or in an HTML email in an attempt to
fool users into accepting unsafe file types from a trusted
source. This vulnerabilty affects both IE 5.5 and 6.0.
Mitigating Factors:
====================
File Execution Vulnerability:
- The vulnerability could not be exploited if File Downloads have
been disabled in the Security Zone from which the file is being
received. In most attempts to maliciously exploit this
vulnerability the file would be received from the Internet or
Intranet zone. Therefore, disabling File Downloads in these zones
can protect customers. This is not the default setting for either
of these zone, however.
- This affects IE 6.0 only.
Frame Domain Verification Variant:
- The vulnerability could only be used to view files. It could not
be used to create, delete, modify or execute them.
- The vulnerability would only allow an attacker to read files that
can be can be opened in a browser window, such as image files,
HTML files and text files. Other file file types, such as binary
files, executable files, Word documents, and so forth, could not
be read.
- The attacker would have to have knowledge of the exact file name
and location in other to successfully read the file on the
local system.
File Name Spoofing Vulnerability:
- The determination on choosing to accept a file download from an
Internet site should always be based on the trustworthiness of
the source and not on the file type. File downloads should never
be accepted from an untrusted source, no matter how harmless the
type may appear to be.
Risk Rating:
============
- 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/ms01-058.asp
for information on obtaining this patch.
Acknowledgment:
===============
- Jouko Pynnonen of Oy Online Solutions Ltd
(http://www.solutions.fi/index.cgi/?lang=eng)
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THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS
PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS
ALL
WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
IN NO EVENT
SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY
DAMAGES
WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL,
LOSS OF
BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR
ITS
SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME
STATES DO
NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL
OR
INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.
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