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Cumulative Security Update for Internet Explorer (MS07-057)
------------------------------------------------------------------------
SUMMARY
The vulnerability with the most serious security impact 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.
DETAILS
Affected Software:
* Internet Explorer 5.01 and Internet Explorer 6 Service Pack 1
* Microsoft Windows 2000 Service Pack 4
* Microsoft Internet Explorer 5.01 Service Pack 4
* Microsoft Windows 2000 Service Pack 4
* Microsoft Internet Explorer 6 Service Pack 1
* Internet Explorer 6
* Windows XP Service Pack 2
* Windows XP Professional x64 Edition and Windows XP Professional x64
Edition Service Pack 2
* Windows Server 2003 Service Pack 1 and Windows Server 2003 Service Pack
2
* Windows Server 2003 x64 Edition and Windows Server 2003 x64 Edition
Service Pack 2
* Windows Server 2003 with SP1 for Itanium-based Systems and Windows
Server 2003 with SP2 for Itanium-based Systems
* Windows XP Service Pack 2
* Windows Internet Explorer 7
* Windows XP Professional x64 Edition and Windows XP Professional x64
Edition Service Pack 2
* Windows Server 2003 Service Pack 1 and Windows Server 2003 Service Pack
2
* Windows Server 2003 x64 Edition and Windows Server 2003 x64 Edition
Service Pack 2
* Windows Server 2003 with SP1 for Itanium-based Systems and Windows
Server 2003 with SP2 for Itanium-based Systems
* Windows Vista
* Windows Vista x64 Edition
Address Bar Spoofing Vulnerability - CVE-2007-3892:
A spoofing vulnerability exists in Internet Explorer that could allow an
attacker to display spoofed content in a browser window. The address bar
and other parts of the trust UI has been navigated away from the attacker
s Web site but the content of the window still contains the attacker s Web
page.
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-2007-3892>
CVE-2007-3892.
Mitigating Factors for Address Bar Spoofing Vulnerability - CVE-2007-3892:
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 would have to host a Web
site that contains a Web page that is used to exploit this vulnerability.
An attacker would have no way to force users to visit a malicious Web
site. Instead, an attacker would have to persuade them to visit the Web
site, typically by getting them to click a link that takes them to the
attacker's Web site.
* The Restricted sites zone helps reduce attacks that could try to
exploit this vulnerability by preventing Active Scripting from being used
when reading HTML e-mail messages. However, if a user clicks a link in an
e-mail message, they could still be vulnerable to this issue through the
Web-based attack scenario.
* By default, all supported versions of Microsoft Outlook and Microsoft
Outlook Express open HTML e-mail messages in the Restricted sites zone.
The Restricted sites zone helps reduce the number of successful attacks
that exploit this vulnerability by preventing Active Scripting and ActiveX
controls from being used when reading HTML e-mail. However, if a user
clicks on a link within an e-mail, they could still be vulnerable to this
issue through the Web-based attack scenario.
* By default, Internet Explorer on Windows Server 2003 runs in a
restricted mode that is known as Enhanced Security Configuration. This
mode mitigates this vulnerability. See the FAQ subsection of this
vulnerability section for more information about Internet Explorer
Enhanced Security Configuration
FAQ for Address Bar Spoofing Vulnerability - CVE-2007-3892:
What is the scope of the vulnerability?
This is a spoofing vulnerability in Internet Explorer. The vulnerability
could allow an attacker to display spoofed content in a browser window.
Interacting with the Web page, for instance, by clicking on it, will cause
the content to refresh and display the Web site pointed out by the address
bar.
What causes the vulnerability?
It is possible to navigate the Internet Explorer address bar and other
parts of the trust User Interface (UI) away from the attacker s Web site.
However, unbeknown to the user, the attacker s site could still be
persisting in the browser window.
How could an attacker exploit the vulnerability?
An attacker could use this vulnerability to create a Web page that would
display a URL of the attacker's choosing in the Address bar, while
displaying a different Web site in the browser window. An attacker could
use this vulnerability to create a malicious page that spoofs a legitimate
site. However, it would not be possible to interact with this same Web
site.
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 does the update do?
The update removes the vulnerability by not allowing the window content to
persist after navigation has occurred.
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.
Error Handling Memory Corruption Vulnerability - CVE-2007-3893:
A remote code execution vulnerability exists in Internet Explorer due to
an unhandled error in certain situations. An attacker could exploit the
vulnerability by constructing a specially crafted Web page. If a user
viewed 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-2007-3893>
CVE-2007-3893.
Mitigating Factors for Error Handling Memory Corruption Vulnerability -
CVE-2007-3893:
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.
* 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.
* By default, all supported versions of Microsoft Outlook and Microsoft
Outlook Express open HTML e-mail messages in the Restricted sites zone.
The Restricted sites zone helps reduce attacks that could try to exploit
this vulnerability by preventing Active Scripting and ActiveX controls
from being used when reading HTML e-mail. However, if a user clicks on a
link within an e-mail they could still be vulnerable to this issue through
the Web-based attack scenario.
* By default, Internet Explorer on Windows Server 2003 runs in a
restricted mode that is known as Enhanced Security Configuration. This
mode sets the security level for the Internet zone to High. This is a
mitigating factor for Web sites that have not been added to Internet
Explorer Trusted sites zone. See the FAQ subsection of this vulnerability
section for more information about Internet Explorer Enhanced Security
Configuration.
Workarounds for Error Handling Memory Corruption Vulnerability -
CVE-2007-3893:
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:
* 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 Error Handling Memory Corruption Vulnerability - CVE-2007-3893:
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.
If a user is logged on with administrative user rights, an attacker who
successfully exploited this vulnerability could take complete control of
an affected system. An attacker could then install programs; view, change,
or delete data; or create new accounts with full user rights. 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.
What causes the vulnerability?
Internet Explorer under certain situations does not correctly handle an
error when determining file downloads in a queue. As a result, system
memory may be corrupted in such a way that an attacker could execute
arbitrary code.
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.
I am running Internet Explorer on Windows Server 2003. Does this mitigate
these vulnerabilities?
Yes. By default, Internet Explorer on Windows Server 2003 runs in a
restricted mode that is known as Enhanced Security Configuration. This
mode sets the security level for the Internet zone to High. This is a
mitigating factor for Web sites that have not been added to Internet
Explorer Trusted sites zone.
What is the Internet Explorer Enhanced Security Configuration?
Internet Explorer Enhanced Security Configuration is a group of
preconfigured Internet Explorer settings that reduce the likelihood of a
user or of an administrator downloading and running specially crafted Web
content on a server. Internet Explorer Enhanced Security Configuration
reduces this risk by modifying many security-related settings. This
includes the settings on the Security tab and the Advanced tab in the
Internet Options dialog box. Some of the important modifications include
the following:
* Security level for the Internet zone is set to High. This setting
disables scripts, ActiveX controls, Microsoft Java Virtual Machine
(MSJVM), and file downloads.
* Automatic detection of intranet sites is disabled. This setting assigns
all intranet Web sites and all Universal Naming Convention (UNC) paths
that are not explicitly listed in the Local intranet zone to the Internet
zone.
* Install On Demand and non-Microsoft browser extensions are disabled.
This setting prevents Web pages from automatically installing components
and prevents non-Microsoft extensions from running.
* Multimedia content is disabled. This setting prevents music,
animations, and video clips from running.
For more information regarding Internet Explorer Enhanced Security
Configuration, see the guide, Managing Internet Explorer Enhanced Security
Configuration, at the following
<http://www.microsoft.com/downloads/details.aspx?FamilyID=d41b036c-e2e1-4960-99bb-9757f7e9e31b&DisplayLang=en>
Web site.
What does the update do?
The update removes the vulnerability by modifying the script error
exception handling so that there is no attempt made to access the freed
memory.
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.
Address Bar Spoofing Vulnerability - CVE-2007-1091 & CVE-2007-3826:
Spoofing vulnerabilities exist in Internet Explorer that could allow an
attacker to display spoofed content in a browser window. The address bar
and other parts of the trust UI has been navigated away from the attacker
s Web site but the content of the window still contains the attacker s Web
page.
To view these vulnerabilities as a standard entry in the Common
Vulnerabilities and Exposures list, see
<http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2007-1091>
CVE-2007-1091 and
<http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2007-3826>
CVE-2007-3826.
Mitigating Factors for Address Bar Spoofing Vulnerability - CVE-2007-1091
& CVE-2007-3826:
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 would have to host a Web
site that contains a Web page that is used to exploit this vulnerability.
An attacker would have no way to force users to visit a malicious Web
site. Instead, an attacker would have to persuade them to visit the Web
site, typically by getting them to click a link that takes them to the
attacker's Web site.
* The Restricted sites zone helps reduce attacks that could try to
exploit this vulnerability by preventing Active Scripting from being used
when reading HTML e-mail messages. However, if a user clicks a link in an
e-mail message, they could still be vulnerable to this issue through the
Web-based attack scenario.
* By default, all supported versions of Microsoft Outlook and Microsoft
Outlook Express open HTML e-mail messages in the Restricted sites zone.
The Restricted sites zone helps reduce attacks that could try to exploit
this vulnerability by preventing Active Scripting and ActiveX controls
from being used when reading HTML e-mail. However, if a user clicks on a
link within an e-mail they could still be vulnerable to this issue through
the Web-based attack scenario.
* By default, Internet Explorer on Windows Server 2003 runs in a
restricted mode that is known as Enhanced Security Configuration. This
mode mitigates this vulnerabilities. See the FAQ section or this security
update for more information about Internet Explorer Enhanced Security
Configuration.
FAQ for Address Bar Spoofing Vulnerability - CVE-2007-1091 &
CVE-2007-3826:
What is the scope of the vulnerabilities?
These are spoofing vulnerabilities in Internet Explorer. The
vulnerabilities could allow an attacker to display spoofed content in a
browser window.
What causes the vulnerabilities?
It is possible for a user to change the URL in the address bar in Internet
Explorer address bar to navigate away from the attacker s Web site.
However, unbeknown to the user, the attacker s site could still be
persisting in the browser window.
How could an attacker exploit these vulnerabilities?
An attacker could use these vulnerabilities to display a URL in the
Address bar, while displaying a different Web site in the browser window.
An attacker could use these vulnerabilities to create a malicious page
that spoofs a legitimate site.
What systems are primarily at risk from these vulnerabilities?
These vulnerabilities require 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 does the update do?
The update removes the vulnerabilities by not allowing the window content
to persist after navigation has occurred.
When this security bulletin was issued, had this vulnerability been
publicly disclosed?
Yes. These vulnerabilities have been publicly disclosed. The first
vulnerability has been assigned Common Vulnerability and Exposure number
CVE-2007-1091 and is named MSIE7 browser entrapment vulnerability by the
larger security community. The second vulnerability has been assigned
Common Vulnerability and Exposure number CVE-2007-3826 and is named MSIE7
entrapment again (+ FF tidbit) by the larger security community.
When this security bulletin was issued, had Microsoft received any reports
that this vulnerabilities was being exploited?
No. Microsoft had not received any information to indicate that these
vulnerabilities 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.
ADDITIONAL INFORMATION
The information has been provided by Microsoft Security Bulletin MS07-057.
The original article can be found at:
<http://www.microsoft.com/technet/security/bulletin/ms07-057.mspx?pubDate=2007-10-09>
http://www.microsoft.com/technet/security/bulletin/ms07-057.mspx?pubDate=2007-10-09
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