SEC-CONSULT Security Advisory < 20060613-0 >

              title: HTML Code Injection in Outlook Web Access
            program: Outlook Web Access
 vulnerable version: Exchange 2000 (SP3), 2003 (SP1), 2003 (SP2)
             impact: severe
           homepage: http://www.microsoft.com/exchange/default.mspx
              found: 2005-10-25
                 by: D. Fabian / SEC-CONSULT / www.sec-consult.com
                     T. Kerbl / SEC-CONSULT / www.sec-consult.com

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vendor description:

Microsoft Office Outlook Web Access is an integrated component of
Exchange Server 2000/2003. By using only a Web browser and an Internet
or intranet connection, Outlook Web Access enables users to read their
corporate e-mail messages, schedules, and other information that is
stored on a server running Exchange.

[Source: http://www.microsoft.com/exchange/evaluation/features/
owa2k3_55.mspx]

vulnerability overview:

Microsoft Outlook Web Access is vulnerable to an HTML code
injection/cross site scripting attack. A malicous user could craft a
mail containing HTML and Javascript code. Such code could be used to
steal session information from the victims cookies, and thus enable
the attacker to get access to the victim's emails.

In alternative Browsers like Mozilla Firefox or Opera the mere opening
of an crafted email is enough for Javascript code to execute. As soon
as the victim clicks on the malicious email, the Javascript code can
read session information and send this to the attacker, who can
then perform session highjacking and read the victims emails.

As Internet Explorer uses proprietary security mechanisms (mails
are displayed as pages in restricted security zone) it is not
possible to inject Javascript code directly into email bodies.
However our research showed, that using HTML attachments (which are
also subject to input sanitation in OWA), the Javascript Code can be
successfully executed. Furthermore HTML Code injection is still
possible directly in the email body. This can be used e.g. by
malicious attackers to include images which are displayed without
further user interaction and thus verify whether the user read the
email or not. Also links can be directly included, curcumventing
OWA's redirection feature.

vulnerability details:

To allow time to Microsoft Exchange administrators to patch their
systems, SEC Consult is going to withhold vulnerability and exploit
details for 2 weeks.

vulnerable versions:

The following versions of Microsoft Exchange Server are vulnerable
to the described security flaw:

• Microsoft Exchange 2000 Server Pack 3 with the August 2004
  Exchange 2000 Server Post-Service Pack 3 Update Rollup
• Microsoft Exchange Server 2003 Service Pack 1
• Microsoft Exchange Server 2003 Service Pack 2

vendor status:

vendor notified: 2005-10-27
vendor response: 2005-10-27
patch available: 2006-06-13

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Mail: office at sec-consult dot com
www.sec-consult.com

EOF Daniel Fabian / @2006
research at sec-consult dot com

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