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Executing Arbitrary Script with mhtml: Protocol Handler (MS07-034)
------------------------------------------------------------------------
SUMMARY
In Internet Explorer, with mhtml: protocol handler and using Outlook
Express's feature, arbitrary resources (such as HTML, image, application
file and so on) can opened as MHTML formatted file and Content-Type: is
disregarded.
It is possible to treat by text/html including JavaScript encoded base64
or Quoted-Printable in MHTML format. Therefore, it was possible to have
bypassed filtering of the dangerous character (or string) usually carried
out in the Web application of the large range, and to have execute
arbitrary scripts.
DETAILS
In IE, When the prefix of "mhtml" is given to the URL and it accesses a
resource, the function of OE is used( mhtml protocol handler is called),
and IE deals with that resource as a MHTML(RFC2557) formatted document.
The behavior of IE is peculiar as follows when a document is opened as a
MHTML form through mhtml: protocol handler.
* Content-Type: HTTP response header is ignored.
* It doesn't depend on the setting "Open files based on content, not file
extension", and "MHTML" is always forced as a file type for the resource.
* In the MHTML document, Separated from the MHTML header by a MHTML body
by the CR/LF in HTTP response body.
* In the MHTML document, encoding by base64 or Quoted-Printable can be
used for the MHTML body part by specifying it with a MHTML header.
* In the MHTML document, text/html document type can be used for the
MHTML body part by specifying it with a MHTML header and can be included
script in the body part.
* "Content-Disposition: attachment" HTTP response header is ignored, and
the resource is opened without user's confirmation.
Therefore, even if it was it to the Web application that it coped with it
suitably, script was put in the form encoded with base64 and
Quoted-Printable inside, and it was possible that XSS was made to occur.
For example,
--
Subject: test
Content-Type: text/html; charset=us-ascii
Content-Transfer-Encoding: base64
PGh0bWw+DQo8c2NyaXB0PmFsZXJ0KGRvY3VtZW50LmxvY2F0aW9uKTs8L3NjcmlwdD4NCjwv
aHRtbD4NCg==
--
Open this HTML file through the mhtml: protocol handler such as , IE/OE
assumed the file as MHTML, not HTML, including script encoded by base64.
The script is encoded by base64, Because it is being encoded with base64,
script passes through the web application's filter, and it is possible
that XSS is made to occur.
In order to ignore Content-Type: header completely, includes the MHTML
contents, it was possible even in XML, images, application file like as
*.doc, and the like not only HTML to execute the script.
Background:
May 2004
The publication by the first discoverer (probably). (Japanese contents)
http://web.archive.org/web/20040607114853/www2.sala.or.jp/~uuu/security/jpeg1.html
Jul 2004
Article of Slashdot Japan "Many Unmeasured vulnerability discovered in
Japan" is published. (Japanese contents)
http://slashdot.jp/security/article.pl?sid=04/07/29/0635211
Feb 2005
[Full-Disclosure] Possible XSS issue on Windows XPSP2 IE6 via MIME
Encapsulation of Aggregate HTML
http://lists.grok.org.uk/pipermail/full-disclosure/2005-February/032058.html
Sep 2006
Ask to grasp it as a vulnerability in Microsoft about this.
Oct 2006
Response from Microsoft, "Behavior by design of IE".
Oct 2006
Report to Microsoft that the XSS is made to occur and can steel Cookie by
using this behavior on on search.microsoft.com / search.live.com /
search.msn.com.
Oct 2006
Report to Microsoft via IPA/ISEC as the vulnerability of Web application
that the XSS is made to occur and can steel Cookie by using this behavior
on on spaces.live.com / msn.co.jp.
Oct 2006
Report to Microsoft via IPA/ISEC as the vulnerability of IE, about the
"Content-Disposition: attachment" header is ignored via mhtml: protocol
handler.
Dec 2006
Received the contact to deal with handling this case as a vulnerability of
OE from Microsoft via IPA/ISEC.
Jun 2007
Security fix for OE released as MS07-034.
CVE Information:
<http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2007-2225>
CVE-2007-2225,
<http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2007-2227>
CVE-2007-2227
ADDITIONAL INFORMATION
The information has been provided by <mailto:yosuke.hasegawa@gmail.com>
HASEGAWA Yosuke.
The original article can be found at:
<http://openmya.hacker.jp/hasegawa/security/ms07-034.txt>
http://openmya.hacker.jp/hasegawa/security/ms07-034.txt
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