Security World: [NT] Cumulative Security Update for Internet Explorer (MS07-045)

The following security advisory is sent to the securiteam mailing list, and can be found at the SecuriTeam web site: http://www.securiteam.com
- - promotion

The SecuriTeam alerts list - Free, Accurate, Independent.

Get your security news from a reliable source.
http://www.securiteam.com/mailinglist.html

- - - - - - - - -

Cumulative Security Update for Internet Explorer (MS07-045)
------------------------------------------------------------------------

SUMMARY

This critical security update resolves three privately reported
vulnerabilities. These vulnerabilities could allow remote code execution
if a user viewed a specially crafted Web page using Internet Explorer.
Users whose accounts are configured to have fewer user rights on the
system could be less impacted than users who operate with administrative
user rights.

The security update is rated critical for supported releases of Internet
Explorer 5.01 and Internet Explorer 6 Service Pack 1. For Internet
Explorer 6 for supported versions and editions of Windows XP Home and
Windows XP Professional, the security update is also rated critical,
otherwise it is rated moderate for other supported operating systems. For
Internet Explorer 7 for supported versions and editions of Windows XP and
Windows XP Professional, and Internet Explorer 7 in Windows Vista, the
security update is rated Important, otherwise it is rated low.

DETAILS

CSS Memory Corruption Vulnerability - CVE-2007-0943:

A remote code execution vulnerability exists in the way Internet Explorer
parses certain strings in CSS. An attacker could exploit the vulnerability
by constructing a specially crafted Web page. When a user views the Web
page, the vulnerability could allow remote code execution. An attacker who
successfully exploited this vulnerability could gain the same user rights
as the logged on user..

To view this vulnerability as a standard entry in the Common
Vulnerabilities and Exposures list, see
<http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2007-0943>
CVE-2007-0943.

Mitigating Factors for CSS Memory Corruption Vulnerability -
CVE-2007-0943:
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:

* In a Web-based attack scenario, an attacker could host a Web site that
contains a Web page that is used to exploit this vulnerability. In
addition, compromised Web sites and Web sites that accept or host
user-provided content or advertisements could contain specially crafted
content that could exploit this vulnerability. In all cases, however, an
attacker would have no way to force users to visit these Web sites.
Instead, an attacker would have to persuade users to visit the Web site,
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.

* An attacker who successfully exploited this vulnerability could gain
the same user rights as the local user. Users whose accounts are
configured to have fewer user rights on the system could be less impacted
than users who operate with administrative user rights.

* Internet Explorer 6 and 7 are not affected by this vulnerability.

FAQ for CSS Memory Corruption Vulnerability - CVE-2007-0943:
What is the scope of the vulnerability?
This is a remote code execution vulnerability. An attacker who
successfully exploited this vulnerability could gain the same user rights
as the logged on user.

What causes the vulnerability?
When Internet Explorer parses certain CSS strings under certain
conditions, memory may be corrupted in such a way that an attacker could
execute arbitrary code in the context of the logged-on user.

What might an attacker use the vulnerability to do?
An attacker who successfully exploited this vulnerability could gain the
same user rights as the logged on user. Users whose accounts are
configured to have fewer user rights on the system could be less impacted
than users who operate with administrative user rights.

How could an attacker exploit the vulnerability?
An attacker could host a specially crafted Web site that is designed to
exploit this vulnerability and then persuade a user to view the Web site.
This can also include compromised Web sites and Web sites that accept or
host user-provided content or advertisements. These Web sites could
contain specially crafted content that could exploit this vulnerability.
In all cases, however, an attacker would have no way to force users to
visit these Web sites. Instead, an attacker would have to persuade users
to visit the Web site, typically by getting them to click a link in an
e-mail message or in an Instant Messenger request that takes users to the
attacker's Web site. It could also be possible to display specially
crafted Web content by using banner advertisements or by using other
methods to deliver Web content to affected systems.

What systems are primarily at risk from the vulnerability?
This vulnerability requires that a user is logged on and visits a Web site
for any malicious action to occur. Therefore, any systems where Internet
Explorer is used frequently, such as workstations or terminal servers, are
at the most risk from this vulnerability.

What is CSS?
CSS or Cascading Style Sheets is a formatting method for Web pages using
HTML. For more information about CSS, visit the Microsoft TechNet Web
site.

What does the update do?
The update prevents memory corruption when Internet Explorer parses CSS
text.

When this security bulletin was issued, had this vulnerability been
publicly disclosed?
No. Microsoft received information about this vulnerability through
responsible disclosure.

When this security bulletin was issued, had Microsoft received any reports
that this vulnerability was being exploited?
No. Microsoft had not received any information to indicate that this
vulnerability had been publicly used to attack customers and had not seen
any examples of proof of concept code published when this security
bulletin was originally issued.

ActiveX Object Vulnerability - CVE-2007-2216:
A remote code execution vulnerability exists in the ActiveX control,
tblinf32.dll. This control can also be found under the name of
vstlbinf.dll. Both of these components were never intended to be supported
in Internet Explorer. An attacker could exploit the vulnerability by
constructing a specially crafted Web page that could potentially allow
remote code execution if a user visited the Web page. An attacker who
successfully exploited this vulnerability could gain the same user rights
as the logged on user.

To view this vulnerability as a standard entry in the Common
Vulnerabilities and Exposures list, see
<http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2007-2216>
CVE-2007-2216.

Mitigating Factors for ActiveX Object Vulnerability - CVE-2007-2216:
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:

* In a Web-based attack scenario, an attacker could host a Web site that
contains a Web page that is used to exploit this vulnerability In
addition, compromised Web sites and Web sites that accept or host
user-provided content could contain specially crafted content that could
exploit this vulnerability. In all cases, however, an attacker would have
no way to force users to visit these Web sites. Instead, an attacker would
have to convince users to visit the Web site, typically by getting them to
click a link in an e-mail or Instant Messenger message that takes users to
the attacker's Web site.

Workarounds for ActiveX Object Vulnerability - CVE-2007-2216:
Workaround refers to a setting or configuration change that does not
correct the underlying vulnerability but would help block known attack
vectors before you apply the update. Microsoft has tested the following
workarounds and states in the discussion whether a workaround reduces
functionality:

* Prevent COM objects from running in Internet Explorer

You can disable attempts to instantiate a COM object in Internet Explorer
by setting the kill bit for the control in the registry.

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.

For detailed steps that you can use to prevent a control from running in
Internet Explorer, see Microsoft Knowledge Base Article 240797. Follow
these steps in this article to create a Compatibility Flags value in the
registry to prevent a COM object from being instantiated in Internet
Explorer.

Note The Class Identifiers and corresponding files where the COM objects
are contained are documented under What does the update do? in the FAQ
for ActiveX Object Vulnerability - CVE-2007-2216 subsection. Replace
{XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX} below with the Class Identifiers
found in that FAQ subsection.

To set the kill bit for a CLSID with a value of
{XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX}, paste the following text in a text
editor such as Notepad. Then, save the file by using the .reg file name
extension.

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\ActiveX
Compatibility\{ XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX }]
"Compatibility Flags"=dword:00000400

* Group Policy collection

* What is Group Policy Object Editor?

* Core Group Policy tools and settings

Note You must restart Internet Explorer for your changes to take effect.

Impact of Workaround: There is no impact as long as the object is not
intended to be used in Internet Explorer.

* Set Internet and Local intranet security zone settings to High to
prompt before running ActiveX Controls and Active Scripting in these zones

You can help protect against this vulnerability by changing your settings
for the Internet security zone to prompt before running ActiveX controls.
You can do this by setting your browser security to High.

To raise the browsing security level in Microsoft Internet Explorer,
follow these steps:
1. On the Internet Explorer Tools menu, click Internet Options.
2. In the Internet Options dialog box, click the Security tab, and then
click the Internet icon.
3. 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 prompting before running
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. Prompting before running ActiveX Controls or
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 ActiveX Controls or 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:

1. In Internet Explorer, click Tools, click Internet Options, and then
click the Security tab.
2. In the Select a Web content zone to specify its current security
settings box, click Trusted Sites, and then click Sites.
3. 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.
4. In the Add this Web site to the zone box, type the URL of a site that
you trust, and then click Add.
5. Repeat these steps for each site that you want to add to the zone.
6. 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
computer. 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.

FAQ for ActiveX Object Vulnerability - CVE-2007-2216:
What is the scope of the vulnerability?
This is a remote code execution vulnerability. An attacker who
successfully exploited this vulnerability could gain the same user rights
as the logged on user.

What causes the vulnerability?
The control implemented IObjectsafety incorrectly. For more information
about IObjectsafety, visit the Microsoft TechNet Web site

What might an attacker use the vulnerability to do?
An attacker who successfully exploited this vulnerability could gain the
same user rights as the local user. Users whose accounts are configured to
have fewer user rights on the system could be less impacted than users who
operate with administrative user rights.

How could an attacker exploit the vulnerability?
An attacker could host a specially crafted Web site that is designed to
exploit this vulnerability through Internet Explorer and then convince a
user to view the Web site. This can also include compromised Web sites and
Web sites that accept or host user-provided content or advertisements.
These Web sites could contain specially crafted content that could exploit
this vulnerability. In all cases, however, an attacker would have no way
to force users to visit these Web sites. Instead, an attacker would have
to convince users to visit the Web site, typically by getting them to
click a link in an e-mail message or in an Instant Messenger request that
takes users to the attacker's Web site. It could also be possible to
display specially crafted Web content by using banner advertisements or by
using other methods to deliver Web content to affected systems.

What systems are primarily at risk from the vulnerability?
This vulnerability requires that a user be logged on and visit a Web site
for any malicious action to occur. Therefore, any systems where Internet
Explorer is used frequently, such as workstations or terminal servers, are
at the most risk from this vulnerability.

What is the ActiveX opt-in feature in Windows Internet Explorer 7?
Windows Internet Explorer 7 includes an ActiveX opt-in feature, which
means that nearly all pre-installed ActiveX controls are off by default.
Users are prompted by the Information Bar before they can instantiate a
previously installed ActiveX control that has not yet been used on the
Internet. This enables a user to permit or deny access on a
control-by-control basis. For more information about this and other new
features, see the Windows Internet Explorer 7 features page.

What does the update do?
This update sets the kill bit for a list of Class Identifiers (CLSIDs).

The Class Identifiers are as follows:
Class Identifier:
Software:
{8B217746-717D-11CE-AB5B-D41203C10000} Microsoft Visual Basic 6
{8B217752-717D-11CE-AB5B-D41203C10000} Microsoft Visual Basic 6
{8B21775E-717D-11CE-AB5B-D41203C10000} Microsoft Visual Basic 6

When this security bulletin was issued, had this vulnerability been
publicly disclosed?
No. Microsoft received information about this vulnerability through
responsible disclosure.

ActiveX Object Memory Corruption Vulnerability - CVE-2007-3041:
A remote code execution vulnerability exists in the ActiveX object,
pdwizard.ocx. An attacker could exploit the vulnerability by constructing
a specially crafted Web page. When a user views the Web page, the
vulnerability could allow remote code execution. An attacker who
successfully exploited this vulnerability could gain the same user rights
as the logged on user.

To view this vulnerability as a standard entry in the Common
Vulnerabilities and Exposures list, see
<http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2007-3041>
CVE-2007-3041.

Mitigating Factors for ActiveX Object Memory Corruption Vulnerability -
CVE-2007-3041:
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:

Workarounds for ActiveX Object Memory Corruption Vulnerability -
CVE-2007-3041:
Workaround refers to a setting or configuration change that does not
correct the underlying vulnerability but would help block known attack
vectors before you apply the update. Microsoft has tested the following
workarounds and states in the discussion whether a workaround reduces
functionality:

* Prevent COM objects from running in Internet Explorer

You can disable attempts to instantiate a COM object in Internet Explorer
by setting the kill bit for the control in the registry.

Note The Class Identifiers and corresponding files where the COM objects
are contained are documented under What does the update do? in the FAQ
for ActiveX Object Memory Corruption Vulnerability - CVE-2007-3041
subsection. Replace {XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX} below with the
Class Identifiers found in this section.

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\ActiveX
Compatibility\{ XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX }]
"Compatibility Flags"=dword:00000400

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:
* Group Policy collection
* What is Group Policy Object Editor?
* Core Group Policy tools and settings

Note You must restart Internet Explorer for your changes to take effect.

Impact of Workaround: There is no impact as long as the object is not
intended to be used in Internet Explorer.

* Set Internet and Local intranet security zone settings to High to
prompt before running ActiveX Controls and Active Scripting in these zones

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

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

To do this, follow these steps:
1. In Internet Explorer, click Tools, click Internet Options, and then
click the Security tab.
2. In the Select a Web content zone to specify its current security
settings box, click Trusted Sites, and then click Sites.
3. 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.
4. In the Add this Web site to the zone box, type the URL of a site that
you trust, and then click Add.
5. Repeat these steps for each site that you want to add to the zone.
6. Click OK two times to accept the changes and return to Internet
Explorer.

FAQ for ActiveX Object Memory Corruption Vulnerability - CVE-2007-3041:
What is the scope of the vulnerability?
This is a remote code execution vulnerability. An attacker who
successfully exploited this vulnerability could gain the same user rights
as the logged on user.

What causes the vulnerability?
When the ActiveX object is used in Internet Explorer, the objects may
corrupt the system state in such a way that an attacker could execute
arbitrary code.

What does the update do?
This update sets the kill bit for a list of Class Identifier (CLSIDs).

The Class Identifier is as follows:
Class Identifier:
Software:
{0DDF3B5C-E692-11D1-AB06-00AA00BDD685} Microsoft Visual Basic
6.0

When this security bulletin was issued, had this vulnerability been
publicly disclosed?
No. Microsoft received information about this vulnerability through
responsible disclosure.

ADDITIONAL INFORMATION

The information has been provided by Microsoft Security Bulletin MS07-045.
The original article can be found at:
<http://www.microsoft.com/technet/security/bulletin/ms07-045.mspx>

http://www.microsoft.com/technet/security/bulletin/ms07-045.mspx

========================================

This bulletin is sent to members of the SecuriTeam mailing list.
To unsubscribe from the list, send mail with an empty subject line and body to: list-unsubscribe@securiteam.com
In order to subscribe to the mailing list, simply forward this email to: list-subscribe@securiteam.com

====================
====================

DISCLAIMER:
The information in this bulletin is provided "AS IS" without warranty of any kind.
In no event shall we be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages.

Security World

Search This Blog

Wednesday, August 15, 2007

[NT] Cumulative Security Update for Internet Explorer (MS07-045)

No comments: