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UNIRAS Brief - 124/04 - iDEFENSE Security Bulletin - Microsoft Outlook "mailto" Parameter Passing Vulnerability


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   UNIRAS (UK Govt CERT) Briefing Notice - 124/04 dated 16.03.04  Time: 11:30  
  UNIRAS is part of NISCC (National Infrastructure Security Co-ordination Centre)
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  UNIRAS material is also available from its website at www.uniras.gov.uk and
         Information about NISCC is available from www.niscc.gov.uk
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iDEFENSE Security Bulletin:

Microsoft Outlook "mailto" Parameter Passing Vulnerability.


On March 10, 2004, Microsoft upgraded the severity of iDEFENSE Security Advisory 
03.09.04 from "Important" to "Critical". This was done as alternate attack vectors 
were uncovered that bypassed the originally proposed workarounds. iDEFENSE is 
re-releasing the advisory to reflect this newly discovered information. 

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Security Bulletin:

On March 10, 2004, Microsoft upgraded the severity of iDEFENSE Security Advisory 
03.09.04 from "Important" to "Critical". This was done as alternate attack vectors 
were uncovered that bypassed the originally proposed workarounds. iDEFENSE is 
re-releasing the advisory to reflect this newly discovered information. Details 
regarding the following information have been added to the Analysis section of 
the advisory:

- - - It is possible for an attacker to force Outlook 2002 to start in the
  "Outlook Today" view.

As a result, the originally proposed workaround of setting the default view to 
something other than "Outlook Today" is not effective.

Pedram Amini
Assistant Director, iDEFENSE Labs

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Microsoft Outlook "mailto:"; Parameter Passing Vulnerability

iDEFENSE Security Advisory 03.09.04 


March 09, 2004


Microsoft Outlook provides an integrated solution for managing and organizing 
e-mail messages, schedules, tasks, notes, contacts, and other information. More 
information is available at http://www.microsoft.com/outlook/.


Insufficient filtering of parameters passed to Microsoft Corp.'s Outlook e-mail 
client via the "mailto:"; URI (RFC 2368) allows for remote script execution within 
the "Local Machine" zone. When Outlook is installed, it is enabled as the default 
e-mail handler. A "mailto:"; URI will spawn Outlook with the following command line 

    OUTLOOK.EXE -c IPM.Note /m "...

The problem manifests when the string '"' is interspersed within the URI, 
thereby allowing an attacker to manipulate the command line switches that Outlook 
is instantiated with. The following example URI:

    ... mailto:aa" /profile "xx" ...

causes Internet Explorer to start Outlook as such:

    OUTLOOK.EXE -c IPM.Note /m "aa" /profile "xx"

The provided URI can be of the form 'javascript:...', allowing an attacker to 
execute arbitrary script code. In some implementations, this script code executes 
under the context of the "Local Machine Zone". An attacker does not need to socially 
engineer a target user into clicking on a malicious link, as the process can be 
started automatically by embedding the "mailto:"; URI within an HTML IMG tag.


Successful exploitation allows an attacker to remotely execute arbitrary code under 
the context of the "Local Machine" zone. Script code executing with such privileges 
can be crafted to retrieve and execute arbitrary third-party code, thereby leading 
to further compromise.

Microsoft had originally stated that only users who had set "Outlook Today" as their 
default Outlook folder home page were affected. Further analysis has revealed that 
users are not protected by changing their default view. Additional manipulation allows 
an attacker to force Outlook to start within the "Outlook Today" view with a specified 
URI. This can be accomplished by first starting Outlook while specifying "Outlook Today" 
as the starting view and then passing in a URI via the '/recycle' command line switch. 
Another potential exploit vector may involve the usage of the command line 
switch '/select outlook:outlook%20today'.

iDEFENSE has proof of concept exploit code demonstrating the impact of this vulnerability.


iDEFENSE has confirmed the existence of this vulnerability in Microsoft Outlook 2002.


iDEFENSE is currently unaware of any valid workarounds.


Microsoft has released the following patches to address this issue:

Microsoft Office XP Service Pack 3




The Mitre Corp.'s Common Vulnerabilities and Exposures (CVE) Project has assigned 
CAN-2004-0121 to this issue.


October  10, 2003   Vulnerability acquired by iDEFENSE
November 12, 2003   Initial vendor notification
November 12, 2003   Initial vendor response
November 21, 2003   iDEFENSE clients notified
March    09, 2004   Coordinated public disclosure
March    11, 2004   Updated advisory


Jouko Pynnönen (http://iki.fi/jouko) is credited with this discovery.

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UNIRAS wishes to acknowledge the contributions of iDEFENSE for the information 
contained in this Briefing. 
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This Briefing contains the information released by the original author. Some 
of the information may have changed since it was released. If the vulnerability 
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<End of UNIRAS Briefing>

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