Vulnerability Note VU#682825

Microsoft Windows "MHTML" protocol handler fails to properly interpret HTTP header

Overview

Microsoft Windows "MHTML" protocol handler fails to properly interpret HTTP headers, which may cause information disclosure.

I. Description

The Microsoft Windows "MHTML" protocol handler contains an information disclosure vulnerability in the way that it interprets HTTP headers. The "MHTML" protocol handler fails to properly interpret HTTP headers when returning MHTML content, which may allow Internet Explorer to bypass Internet Explorer domain restrictions.

II. Impact

By convincing a user to visit a specially crafted website, a remote, unauthenticated attacker may be able to access sensitive information.

III. Solution

Apply an update

This issue is addressed by Microsoft Security Bulletin MS07-034.

Workarounds

Microsoft has provided the following workarounds to address this issue:

Disable the MHTML protocol handler.

1. Click Start and then click Run. Enter regedit.exe in the text box and click OK.
2. Navigate to HKEY_CLASSES_ROOTCLSID{05300401-BCBC-11d0-85E3-00C04FD85AB4}.
3. Right click {05300401-BCBC-11d0-85E3-00C04FD85AB4} and select Permissions.
4. Click Advanced.
5. Uncheck Allow inheritable permissions from the parent to propagate…
6. Click Remove, and then click OK. Click Yes and OKon subsequent screens.
Impact of workaround: This workaround disables page rendering for MHTML Web pages.


Configure Internet Explorer to prompt before running Active Scripting or to disable Active Scripting in the Internet and Local intranet security zone.

1. In Internet Explorer, click Internet Options on the Tools menu.
2. Click the Security tab.
3. Click Internet, and then click Custom Level.
4. Under Settings, in the Scripting section, under Active Scripting, click Prompt or Disable, and then click OK.
5. Click Local intranet, and then click Custom Level.
6. Under Settings, in the Scripting section, under Active Scripting, click Prompt or Disable, and then click OK.
7. Click OK two times to return to Internet Explorer.

Please see Microsoft Security Bulletin MS07-034 for further details.

Systems Affected

Vendor	Status	Date Updated
Microsoft Corporation	Vulnerable	13-Jun-2007

References

http://www.microsoft.com/technet/security/bulletin/ms07-034.mspx
http://secunia.com/advisories/25639/

Credit

This vulnerability was reported in Microsoft Security Bulletin MS07-034. Microsoft thanks SANS ISC for their assistance.

This document was written by Katie Steiner.

Other Information

Date Public	06/12/2007
Date First Published	06/13/2007 04:09:34 PM
Date Last Updated	06/21/2007
CERT Advisory
CVE Name	CVE-2007-2225
Metric	0.00
Document Revision	9