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Title: IE can Divulge Location of Cached Content
Date: 06 March 2001
Software: IE and Windows Scripting Host
Impact: Run code of attacker's choice. Three other
vulnerabilities, of lesser severity and exploitable in
more restricted circumstances, also are eliminated by
the patches.
Bulletin: MS01-015

Microsoft encourages customers to review the Security Bulletin at:
http://www.microsoft.com/technet/security/bulletin/MS01-015.asp.

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Issue:

The IE security architecture provides a caching mechanism that is
used to store content that needs to be downloaded and processed on
the user's local machine. The purpose of the cache is to obfuscate
the physical location of the cached content, in order to ensure that
the web page or HTML e-mail will work through the IE security
architecture to access the information. This ensures that the uses
of the information can be properly restricted.

A vulnerability exists because it is possible for a web page or HTML
e-mail to learn the physical location of cached content. Armed with
this information, an attacker could cause the cached content to be
opened in the Local Computer Zone. This would enable him to launch
compiled HTML help (.CHM) files that contain shortcuts to
executables, thereby enabling him to run the executables.

In addition to eliminating this vulnerability, the patches provided
below eliminate three other vulnerabilities that either pose
significantly less risk or could only be exploited in very
restricted situations:

• A variant of the "Frame Domain Verification" vulnerability
  discussed in Microsoft Security Bulletins MS00-033, MS00-055,
  and MS00-093. 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.
• A vulnerability that is identical in effect to the "Frame
  Domain Verification" vulnerability, but which actually results
  from a flaw in Windows Scripting Host rather than IE. Because
  it could only be exploited via IE, we have provided the patch
  here.
• A vulnerability that affects how Telnet sessions are invoked
  via IE. By design, telnet sessions can be launched via IE.
  However, a vulnerability exists because when doing so, IE will
  start Telnet using any command-line options the web site
  specifies. This only becomes a concern when using the version
  of the Telnet client that installs as part of Services for
  Unix (SFU) 2.0 on Windows NT(r) 4.0 or Windows(r) 2000
  machines. The version of the Telnet client in SFU 2.0 provides
  an option for creating a verbatim transcript of a Telnet
  session. An attacker could start a session using the logging
  option, then stream an executable file onto the user's system
  in a location that would cause it to be executed automatically
  the next time the user booted the machine. The flaw does not
  lie in the Telnet client, but in IE, which should not allow
  Telnet to be started remotely with command-line arguments.

Mitigating Factors:

• None of the vulnerabilities could be exploited without some
  user action - either browsing to the attacker's site or opening
  a mail from him. Customers who exercise safe browsing habits
  would be less likely visit untrustworthy sites, and customers
  who have used the Security Zones feature to restrict what HTML
  mail can do would be less likely to be affected by this
  vulnerability.
• The variants of the "frame domain verification" vulnerability
  discussed above could only be used to view files, and only file
  types that can be opened in a browser window.
• The vulnerability affecting Telnet invocation is only a concern
  for customers who are using the Telnet client that ships as
  part of Services for Unix 2.0. Other versions of Telnet do not
  include the command-line feature to create log files.

Patch Availability:

• A patch is available to fix this vulnerability. Please read the
  Security Bulletin
  http://www.microsoft.com/technet/security/bulletin/ms01-015.asp
  for information on obtaining this patch.

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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,
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OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO
THE FOREGOING LIMITATION MAY NOT APPLY.

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