(Microsoft Issues Fix for OWC) Microsoft Office Web Components Let Remote Users Write Code to Run in the Victim's Local Security Domain and Access Local or Remote Files
SecurityTracker Alert ID: 1005102|
SecurityTracker URL: http://securitytracker.com/id/1005102
(Links to External Site)
Date: Aug 21 2002
Disclosure of system information, Disclosure of user information, Execution of arbitrary code via network|
Fix Available: Yes Vendor Confirmed: Yes |
Version(s): OWC 2000, OWC 2002|
GreyMagic Software has issued several advisories warning of scripting vulnerabilities in Microsoft Office due to flaws in Microsoft's Office Web Components. In this advisory, they indicate that remotely supplied HTML can cause Internet Explorer read local files.|
Several vulnerabilities were reported in Microsoft's Office Web Components (OWC), which is included in Microsoft Office but is also available as a standalone viewer. OWC is reported to be a group of components marked as of 'safe for scripting' and used to enrich HTML documents with spreadsheets, charts, pivot tables and more.
A remote user can apparently exploit OWC9 and OWC10 to cause IE to ready any local or remote file via the "LoadText" method of the Range object. If the URL supplied to this method is not the same security domain as the current document, the function apparently returns an error. However, a user can reportedly bypass this restriction by using a URL that will redirect to the desired local or remote file. OWC will then interpret the URL as safe to load and will load the contents of the file into the spreadsheet, according to the advisory.
A demonstration exploit is provided in the Source Message.
The vendor has reportedly been notified.
For more information, see:
A remote user can create HTML containing code that will, when loaded by the target (victim) user, run in the local user security context and be able to retrieve local or remote files.|
The vendor has released a patch.|
Microsoft recommends that Office users install the Office XP SP2 update using the Office poduct Updates site:
The general OWC patch is available at:
For Microsoft Project 2002:
For Microsoft Project Server 2002:
For Office Web Components Download:
The general patch can reportedly be installed on the following systems:
* Microsoft BackOffice Server 2000 Gold or later
* Microsoft BizTalk Server 2000 Gold or later
* Microsoft BizTalk Server 2002 Gold or later
* Microsoft Commerce Server 2000 Gold or later
* Microsoft Commerce Server 2002 Gold or later
* Microsoft Internet Security and Acceleration Server 2000 Gold or later
* Microsoft Money 2002 or later
* Microsoft Money 2003 or later
* Microsoft Office 2000 Gold or later
* Microsoft Office XP Gold or later
* Microsoft Project Server 2002 Gold or later
* Microsoft Small Business Server 2000 Gold or later
The Microsoft Project 2002 patch can be installed on Microsoft Project 2002 Gold or later.
The Microsoft Project Server 2002 patch can be installed on Microsoft Project Server 2002 Gold or later.
Microsoft has included this fix in Office XP SP2:
Microsoft plans to issue Knowledge Base article Q328130 regarding this issue, to be available shortly on the Microsoft Online Support web site:
Vendor URL: www.microsoft.com/technet/security/bulletin/MS02-044.asp (Links to External Site)
Access control error|
|Underlying OS: Windows (Any)|
This archive entry is a follow-up to the message listed below.|
Source Message Contents
Subject: Microsoft Security Bulletin MS02-044 : Unsafe Functions in Office Web Components (Q328130)|
-----BEGIN PGP SIGNED MESSAGE-----
Title: Unsafe Functions in Office Web Components (Q328130)
Date: 21 August 2002
Software: Office Web Components, Office, BackOffice Server,
BizTalk Server, Commerce Server, ISA Server, Money,
Microsoft Project, Microsoft Project Server
Small Business Server
Impact: Three vulnerabilities, the most serious of which could
allow an attacker to run commands on the user's system.
Max Risk: Critical
Microsoft encourages customers to review the Security Bulletin at:
The Office Web Components (OWC) contain several ActiveX controls
that give users limited functionality of Microsoft Office in a web
browser without requiring that the user install the full
Microsoft Office application. This allows users to utilize
Microsoft Office applications in situations where installation
of the full application is infeasible or undesirable.
The control contains three security vulnerabilities, each of
which could be exploited either via a web site or an HTML mail.
The vulnerabilities result because of implementation errors
in the following methods and functions the controls expose:
- Host(). This function, by design, provides the caller with
access to applications' object models on the user's system.
By using the Host() function, an attacker could, for instance,
open an Office application on the user's system and invoke
commands there that would execute operating system commands
as the user.
- LoadText(). This method allows a web page to load text into a
browser window. The method does check that the source of the
text is in the same domain as the window, and in theory should
restrict the page to only loading text that it hosts itself.
However, it is possible to circumvent this restriction by
specifying a text source located within the web page's domain,
and then setting up a server-side redirect of that text to a
file on the user's system. This would provide an attacker with
a way to read any desired file on the user's system.
- Copy()/Paste(). These methods allow text to be copied and pasted.
A security vulnerability results because the method does not
respect the "disallow paste via script" security setting in IE.
Thus, even if this setting had been selected, a web page could
continue to access the copy buffer, and read any text that the
user had copied or cut from within other applications.
The patch does not set "kill bit" on the control, for reasons
discussed in the FAQ.
- In the case of the web-based attack, an attacker would need
to force a user to visit the attacker's Web site. Users who
exercise caution in visiting web sites could minimize their
- In the web based attack, If ActiveX controls have been
disabled in the zone in which the page were viewed, the
vulnerability could not be exploited. Users who place
untrusted sites in the Restricted Sites zone, which disables
ActiveX by default, or have disabled ActiveX controls in the
Internet zone could minimize their risk.
- In the case of HTML email based attacks, customers who read
email in the Restricted Sites zone would be protected against
attempts to exploit this vulnerability. Customers using
Outlook 2002 and Outlook Express 6.0, as well as
Outlook 2000 and Outlook 98 customers who have applied the
Outlook Email Security Update would thus be protected by
default. Also, Outlook Express 5.0 customers who have chosen
to read mail in the Restricted Sites zone would be protected
- In the HTML email based attack, Outlook 2002 customers who
have enabled the "Read as Plain Text" option available in
SP1 or later would also be protected.
- The attacker's code would be limited by restrictions on the
user's account. Users of non-privileged accounts would limit
the potential damage from a successful attack.
- The attacker would need to know the full path and name of the
file. In addition the file would have to be viewable in a
- The vulnerability could enable an attacker to access only to
information in the Windows clipboard. The information in the
clipboard is unpredictable and this vulnerability gives no
means for an attacker to target and retrieve specific
information. Further, it is possible for the clipboard to
be empty, which would yield an attacker nothing.
- The security setting in question is not enabled by default.
Thus, the vulnerability does not present a threat to the
- Internet systems: Moderate
- Intranet systems: Moderate
- Client systems: Critical
- A patch is available to fix this vulnerability. Please read the
Security Bulletin at
for information on obtaining this patch.
THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS
PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS
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
WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL,
BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR
SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME
NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL
INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.
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