[MS] Schwachstelle in MHTML

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Liebe Kolleginnen und Kollegen,

soeben erreichte uns nachfolgende Warnung des Microsoft Product Security
Notification Service. Wir geben diese Informationen unveraendert an Sie
weiter.

MHTML (MIME Encapsulation of Aggregate HTML) ist ein Internetstandard
der definiert, wie die MIME-Struktur genutzt wird, um HTML-Inhalt zu
verpacken. Der MHTML-Protokoll-Handler von Windows stellt ein “pluggable
protocol” bereit, dass es erlaubt, Dokumente, die mit MHTML encodiert
wurden, in Applikationen zu rendern.

CVE-2011-0096 – Schwachstelle in MHTML

Durch die Art und Weise wie MHTML MIME-formatierte Anfragen
interpretiert ist es moeglich, dass Skripte, die in der Anfrage
enthalten sind, im falschen Sicherheitskontext ausgefuehrt werden. Ein
entfernter Angreifer kann dies ausnutzen, falls es ihm gelingt einen
Nutzer davon zu ueberzeugen einem praeparierten Link zu folgen, oder
eine praeparierte Datei zu oeffnen. Dadurch ist es moeglich, Skripte in
der Antwort einzufuegen, die vertrauliche Informationen auslesen,
falsche Daten anzeigen oder beliebige Aktionen im Kontext der Webseite
durchfuehren.

Betroffen sind die folgenden Software Pakete und Plattformen:

Microsoft MHTML

Windows XP Service Pack 3
Windows XP Professional x64 Edition Service Pack 2
Windows Server 2003 Service Pack 2
Windows Server 2003 x64 Edition Service Pack 2
Windows Server 2003 mit SP2 fuer Itanium-basierte Systeme
Windows Vista Service Pack 1
Windows Vista Service Pack 2
Windows Vista x64 Edition Service Pack 1
Windows Vista x64 Edition Service Pack 2
Windows Server 2008 fuer 32-bit Systeme
Windows Server 2008 fuer 32-bit Systeme Service Pack 2
Windows Server 2008 fuer x64-basierte Systems
Windows Server 2008 fuer x64-basierte Systems Service Pack 2
Windows Server 2008 fuer Itanium-basierte Systeme
Windows Server 2008 fuer Itanium-basierte Systeme Service Pack 2
Windows 7 fuer 32-bit Systeme
Windows 7 fuer x64-basierte Systeme
Windows Server 2008 R2 fuer x64-basierte Systeme
Windows Server 2008 R2 fuer Itanium-basierte Systeme

Weiterhin existieren Workarounds:

Der Hersteller empfiehlt clientseitig einen Workaround, der im Abschnitt
“Suggested Actions” des Advisories beschrieben ist.

Das Advisory Archiv des Herstellers

http://www.microsoft.com/technet/security/advisory/2501696.mspx

(c) der deutschen Zusammenfassung bei DFN-CERT Services GmbH; die
Verbreitung, auch auszugsweise, ist nur unter Hinweis auf den Urheber,
DFN-CERT Services GmbH, und nur zu nicht kommerziellen Zwecken
gestattet.

Mit freundlichen Gruessen,
Timo Schulz

– —
Timo Schulz, B.Sc. (Incident Response Team)

DFN-CERT Services GmbH, https://www.dfn-cert.de, Phone +49 40 808077-590
Sitz / Register: Hamburg, AG Hamburg, HRB 88805, Ust-IdNr.: DE 232129737
Sachsenstrasse 5, 20097 Hamburg/Germany, CEO: Dr. Klaus-Peter Kossakowski

Automatische Warnmeldungen: https://www.cert.dfn.de/autowarn

Microsoft Security Advisory (2501696)
Vulnerability in MHTML Could Allow Information Disclosure
Published: January 28, 2011

Version: 1.0
General Information
Executive Summary

Microsoft is investigating new public reports of a vulnerability in all supported editions of Microsoft Windows. The vulnerability could allow an attacker to cause a victim to run malicious scripts when visiting various Web sites, resulting in information disclosure. This impact is similar to server-side cross-site scripting (XSS) vulnerabilities. Microsoft is aware of published information and proof-of-concept code that attempts to exploit this vulnerability. At this time, Microsoft has not seen any indications of active exploitation of the vulnerability.

The vulnerability exists due to the way MHTML interprets MIME-formatted requests for content blocks within a document. It is possible under certain conditions for this vulnerability to allow an attacker to inject a client-side script in the response of a Web request run in the context of the victim’s Internet Explorer. The script could spoof content, disclose information, or take any action that the user could take on the affected Web site on behalf of the targeted user.

We are actively working with partners in our Microsoft Active Protections Program (MAPP) to provide information that they can use to provide broader protections to customers.

We are collaborating with Service Providers to investigate server-side workarounds, but we recommend that customers apply one or more of the client-side workarounds provided in the Suggested Actions section of this advisory to help block potential attack vectors regardless of the service.

Upon completion of this investigation, Microsoft will take the appropriate action to help protect our customers. This may include providing a security update through our monthly release process or providing an out-of-cycle security update, depending on customer needs.
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Advisory Details
Issue References

For more information about this issue, see the following references:
References Identification

CVE Reference

CVE-2011-0096

Microsoft Knowledge Base Article

2501696
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Affected and Non-Affected Software

This advisory discusses the following software.
Affected Software

Windows XP Service Pack 3

Windows XP Professional x64 Edition Service Pack 2

Windows Server 2003 Service Pack 2

Windows Server 2003 x64 Edition Service Pack 2

Windows Server 2003 with SP2 for Itanium-based Systems

Windows Vista Service Pack 1 and Windows Vista Service Pack 2

Windows Vista x64 Edition Service Pack 1 and Windows Vista x64 Edition Service Pack 2

Windows Server 2008 for 32-bit Systems and Windows Server 2008 for 32-bit Systems Service Pack 2**

Windows Server 2008 for x64-based Systems and Windows Server 2008 for x64-based Systems Service Pack 2**

Windows Server 2008 for Itanium-based Systems and Windows Server 2008 for Itanium-based Systems Service Pack 2

Windows 7 for 32-bit Systems

Windows 7 for x64-based Systems

Windows Server 2008 R2 for x64-based Systems**

Windows Server 2008 R2 for Itanium-based Systems

**Server Core installation not affected. The vulnerability described in this advisory does not affect supported editions of Windows Server 2008 or Windows Server 2008 R2 as indicated, when installed using the Server Core installation option. For more information on this installation option, see the TechNet articles, Managing a Server Core Installation and Servicing a Server Core Installation. Note that the Server Core installation option does not apply to certain editions of Windows Server 2008 and Windows Server 2008 R2; see Compare Server Core Installation Options.
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Frequently Asked Questions

What is the scope of the advisory?
Microsoft is investigating new public reports of a vulnerability in MHTML on all supported editions of Microsoft Windows. This vulnerability manifests itself in Internet Explorer.

Is this a security vulnerability that requires Microsoft to issue a security update?
Upon completion of this investigation, Microsoft will take the appropriate action to help protect our customers. This may include providing a security update through our monthly release process, or providing an out-of-cycle security update, depending on our customer needs.

What is MHTML?
MHTML (MIME Encapsulation of Aggregate HTML) is an Internet standard that defines the MIME structure that is used to wrap HTML content. The MHTML protocol handler in Windows provides a pluggable protocol (MHTML:) that permits MHTML encoded documents to be rendered in applications.

What causes this threat?
The vulnerability exists due to the way MHTML interprets MIME-formatted requests for content blocks within a document. It is possible for this vulnerability to allow an attacker to run script in the wrong security context.

What might an attacker use this vulnerability to do?
An attacker who successfully exploited this vulnerability could inject a client-side script in the user’s Internet Explorer instance. The script could spoof content, disclose information, or take any action that the user could take on the affected Web site on behalf of the targeted user.

How could an attacker exploit the vulnerability?
In a Web-based attack scenario, an attacker could convince a user to click a specially crafted link that would inject a malicious script in the response of the Web request.
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Mitigating Factors and Suggested Actions

Mitigating Factors

Mitigation refers to a setting, common configuration, or general best-practice, existing in a default state, that could reduce the severity of exploitation of a vulnerability. The following mitigating factors may be helpful in your situation:
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By default, Internet Explorer on Windows Server 2003, Windows Server 2008, and Windows Server 2008 R2 runs in a restricted mode that is known as Enhanced Security Configuration. This mode mitigates this vulnerability.
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By default, all supported versions of Microsoft Outlook, Microsoft Outlook Express, and Windows Mail open HTML e-mail messages in the Restricted sites zone, which disables script and ActiveX controls, removing the risk of an attacker being able to use this vulnerability to execute malicious code. If a user clicks a link in an e-mail message, the user could still be vulnerable to exploitation of this vulnerability through the Web-based attack scenario.
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In a Web-based attack scenario, a Web site could contain a specially crafted link (MHTML:) that is used to exploit this vulnerability. An attacker would have to convince users to visit the Web site and open a specially crafted URL, typically by getting them to click a link in an e-mail message or Instant Messenger message that takes users to the attacker’s Web site, and then convincing them to click the specially crafted link.
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Suggested Actions

Enable the MHTML protocol lockdown

Note Workarounds refer to a setting or configuration change that does not correct the underlying issue but would help block known attack vectors before a security update is available. Microsoft has tested the following workaround and states in the discussion whether the workaround reduces functionality.

Warning If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.

Note See Microsoft Knowledge Base Article 2501696 to use the automated Microsoft Fix it solution to enable and disable this workaround.

To lockdown the MHTML protocol, paste the following text in a text editor such as Notepad. Then, save the file by using the .reg file name extension.

For 32-bit editions of Microsoft Windows:

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\MAIN\FeatureControl\FEATURE_PROTOCOL_LOCKDOWN]
“explorer.exe”=dword:00000001
“iexplore.exe”=dword:00000001
“*”=dword:00000001

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\RestrictedProtocols]

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\RestrictedProtocols\1]
“mhtml”=”mhtml”

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\RestrictedProtocols\2]
“mhtml”=”mhtml”

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\RestrictedProtocols\3]
“mhtml”=”mhtml”

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\RestrictedProtocols\4]
“mhtml”=”mhtml”

For 64-bit editions of Microsoft Windows:

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\MAIN\FeatureControl\FEATURE_PROTOCOL_LOCKDOWN]
“explorer.exe”=dword:00000001
“iexplore.exe”=dword:00000001
“*”=dword:00000001

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\RestrictedProtocols]

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\RestrictedProtocols\1]
“mhtml”=”mhtml”

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\RestrictedProtocols\2]
“mhtml”=”mhtml”

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\RestrictedProtocols\3]
“mhtml”=”mhtml”

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\RestrictedProtocols\4]
“mhtml”=”mhtml”

[HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Internet Explorer\MAIN\FeatureControl\FEATURE_PROTOCOL_LOCKDOWN]
“explorer.exe”=dword:00000001
“iexplore.exe”=dword:00000001
“*”=dword:00000001

[HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Windows\CurrentVersion\Internet Settings\RestrictedProtocols]

[HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Windows\CurrentVersion\Internet Settings\RestrictedProtocols\1]
“mhtml”=”mhtml”

[HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Windows\CurrentVersion\Internet Settings\RestrictedProtocols\2]
“mhtml”=”mhtml”

[HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Windows\CurrentVersion\Internet Settings\RestrictedProtocols\3]
“mhtml”=”mhtml”

[HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Windows\CurrentVersion\Internet Settings\RestrictedProtocols\4]
“mhtml”=”mhtml”

You can apply this .reg file to individual systems by double-clicking it. You can also apply it across domains by using Group Policy. For more information about Group Policy, visit the following Microsoft Web sites:
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Group Policy collection
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What is Group Policy Object Editor
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Core Group Policy tools and settings

Impact of workaround. The MHTML protocol will be restricted to prevent the launch of script in all zones within an MHTML document. Any application that uses MHTML will be affected by this workaround. Script in standard HTML files is not affected by this workaround.

How to undo the workaround. To reverse this workaround, paste the following text in a text editor such as Notepad. Then, save the file by using the .reg file name extension.

For 32-bit editions of Microsoft Windows:

Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\MAIN\FeatureControl\FEATURE_PROTOCOL_LOCKDOWN]
“explorer.exe”=dword:00000000
“iexplore.exe”=dword:00000000

[-HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\RestrictedProtocols]

For 64-bit editions of Microsoft Windows:

[-HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\RestrictedProtocols]

[HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Internet Explorer\MAIN\FeatureControl\FEATURE_PROTOCOL_LOCKDOWN]
“explorer.exe”=dword:00000000
“iexplore.exe”=dword:00000000

[-HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Windows\CurrentVersion\Internet Settings\RestrictedProtocols]

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Set Internet and Local intranet security zone settings to “High” to block ActiveX Controls and Active Scripting in these zones

You can help protect against exploitation of this vulnerability by changing your settings for the Internet security zone to block ActiveX controls and Active Scripting. You can do this by setting your browser security to High.

To raise the browsing security level in Internet Explorer, follow these steps:

On the Internet Explorer Tools menu, click Internet Options.

In the Internet Options dialog box, click the Security tab, and then click the Internet icon.

Under Security level for this zone, move the slider to High. This sets the security level for all Web sites you visit to High.

Note If no slider is visible, click Default Level, and then move the slider to High.

Note Setting the level to High may cause some Web sites to work incorrectly. If you have difficulty using a Web site after you change this setting, and you are sure the site is safe to use, you can add that site to your list of trusted sites. This will allow the site to work correctly even with the security setting set to High.

Impact of workaround. There are side effects to blocking ActiveX Controls and Active Scripting. Many Web sites that are on the Internet or on an intranet use ActiveX or Active Scripting to provide additional functionality. For example, an online e-commerce site or banking site may use ActiveX Controls to provide menus, ordering forms, or even account statements. Blocking ActiveX Controls or Active Scripting is a global setting that affects all Internet and intranet sites. If you do not want to block ActiveX Controls or Active Scripting for such sites, use the steps outlined in “Add sites that you trust to the Internet Explorer Trusted sites zone”.

Add sites that you trust to the Internet Explorer Trusted sites zone

After you set Internet Explorer to block ActiveX controls and Active Scripting in the Internet zone and in the Local intranet zone, you can add sites that you trust to the Internet Explorer Trusted sites zone. This will allow you to continue to use trusted Web sites exactly as you do today, while helping to protect yourself from this attack on untrusted sites. We recommend that you add only sites that you trust to the Trusted sites zone.

To do this, follow these steps:

In Internet Explorer, click Tools, click Internet Options, and then click the Security tab.

In the Select a Web content zone to specify its current security settings box, click Trusted Sites, and then click Sites.

If you want to add sites that do not require an encrypted channel, click to clear the Require server verification (https:) for all sites in this zone check box.

In the Add this Web site to the zone box, type the URL of a site that you trust, and then click Add.

Repeat these steps for each site that you want to add to the zone.

Click OK two times to accept the changes and return to Internet Explorer.

Note Add any sites that you trust not to take malicious action on your system. Two in particular that you may want to add are *.windowsupdate.microsoft.com and *.update.microsoft.com. These are the sites that will host the update, and it requires an ActiveX Control to install the update.
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Configure Internet Explorer to prompt before running Active Scripting or to disable Active Scripting in the Internet and Local intranet security zone

You can help protect against exploitation of this vulnerability by changing your settings to prompt before running Active Scripting or to disable Active Scripting in the Internet and Local intranet security zone. To do this, follow these steps:

In Internet Explorer, click Internet Options on the Tools menu.

Click the Security tab.

Click Internet, and then click Custom Level.

Under Settings, in the Scripting section, under Active Scripting, click Prompt or Disable, and then click OK.

Click Local intranet, and then click Custom Level.

Under Settings, in the Scripting section, under Active Scripting, click Prompt or Disable, and then click OK.

Click OK two times to return to Internet Explorer.

Note Disabling Active Scripting in the Internet and Local intranet security zones may cause some Web sites to work incorrectly. If you have difficulty using a Web site after you change this setting, and you are sure the site is safe to use, you can add that site to your list of trusted sites. This will allow the site to work correctly.

Impact of workaround. There are side effects to prompting before running Active Scripting. Many Web sites that are on the Internet or on an intranet use Active Scripting to provide additional functionality. For example, an online e-commerce site or banking site may use Active Scripting to provide menus, ordering forms, or even account statements. Prompting before running Active Scripting is a global setting that affects all Internet and intranet sites. You will be prompted frequently when you enable this workaround. For each prompt, if you feel you trust the site that you are visiting, click Yes to run Active Scripting. If you do not want to be prompted for all these sites, use the steps outlined in “Add sites that you trust to the Internet Explorer Trusted sites zone”.

Add sites that you trust to the Internet Explorer Trusted sites zone

After you set Internet Explorer to require a prompt before it runs ActiveX controls and Active Scripting in the Internet zone and in the Local intranet zone, you can add sites that you trust to the Internet Explorer Trusted sites zone. This will allow you to continue to use trusted Web sites exactly as you do today, while helping to protect you from this attack on untrusted sites. We recommend that you add only sites that you trust to the Trusted sites zone.

To do this, follow these steps:

In Internet Explorer, click Tools, click Internet Options, and then click the Security tab.

In the Select a Web content zone to specify its current security settings box, click Trusted Sites, and then click Sites.

If you want to add sites that do not require an encrypted channel, click to clear the Require server verification (https:) for all sites in this zone check box.

In the Add this Web site to the zone box, type the URL of a site that you trust, and then click Add.

Repeat these steps for each site that you want to add to the zone.

Click OK two times to accept the changes and return to Internet Explorer.

Additional Suggested Actions
â?¢

Review the Microsoft Knowledge Base Article that is associated with this advisory

For more information about this issue, see Microsoft Knowledge Base Article 2501696.
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Protect your PC

We continue to encourage customers to follow our Protect Your Computer guidance of enabling a firewall, getting software updates and installing antivirus software. Customers can learn more about these steps by visiting Protect Your Computer.

For more information about staying safe on the Internet, visit Microsoft Security Central.
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Keep Windows Updated

All Windows users should apply the latest Microsoft security updates to help make sure that their computers are as protected as possible. If you are not sure whether your software is up to date, visit Windows Update, scan your computer for available updates, and install any high-priority updates that are offered to you. If you have Automatic Updates enabled, the updates are delivered to you when they are released, but you have to make sure you install them.
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Other Information
Microsoft Active Protections Program (MAPP)

To improve security protections for customers, Microsoft provides vulnerability information to major security software providers in advance of each monthly security update release. Security software providers can then use this vulnerability information to provide updated protections to customers via their security software or devices, such as antivirus, network-based intrusion detection systems, or host-based intrusion prevention systems. To determine whether active protections are available from security software providers, please visit the active protections Web sites provided by program partners, listed in Microsoft Active Protections Program (MAPP) Partners.
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Feedback
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You can provide feedback by completing the Microsoft Help and Support form, Customer Service Contact Us.
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Support
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Customers in the United States and Canada can receive technical support from Security Support. For more information about available support options, see Microsoft Help and Support.
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International customers can receive support from their local Microsoft subsidiaries. For more information about how to contact Microsoft for international support issues, visit International Support.
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Microsoft TechNet Security provides additional information about security in Microsoft products.
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Disclaimer

The information provided in this advisory is provided “as is” without warranty of any kind. Microsoft disclaims all 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 damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages, even if Microsoft Corporation or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing limitation may not apply.
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Revisions
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V1.0 (January 28, 2011): Advisory published.

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[MS] Schwachstelle in MHTML - 2501696

LMP003 Chemnitzer Linux-Tage 2026

[MS] Schwachstelle in MHTML – 2501696

[MS] Schwachstelle in MHTML - 2501696