Microsoft Security Bulletin MS15-043 - Critical

Cumulative Security Update for Internet Explorer (3049563)

Published: May 12, 2015

Version: 1.0

Executive Summary

This security update resolves vulnerabilities in Internet Explorer. The most severe of the vulnerabilities could allow remote code execution if a user views a specially crafted webpage using Internet Explorer. An attacker who successfully exploited these vulnerabilities could gain the same user rights as the current user. Customers whose accounts are configured to have fewer user rights on the system could be less impacted than those who operate with administrative user rights.

This security update is rated Critical for Internet Explorer 6 (IE 6), Internet Explorer 7 (IE 7), Internet Explorer 8 (IE 8), Internet Explorer 9 (IE 9), Internet Explorer 10 (IE 10), and Internet Explorer 11 (IE 11) on affected Windows clients, and Moderate for Internet Explorer 6 (IE 6), Internet Explorer 7 (IE 7), Internet Explorer 8 (IE 8), Internet Explorer 9 (IE 9), Internet Explorer 10 (IE 10), and Internet Explorer 11 (IE 11) on affected Windows servers. For more information, see the Affected Software section.

The security update addresses the vulnerabilities by:

• Modifying how Internet Explorer handles objects in memory
• Helping to ensure that affected versions of JScript and VBScript and Internet Explorer properly implement the ASLR security feature
• Adding additional permission validations to Internet Explorer
• Helping to prevent information stored in a user’s clipboard from being accessed by a malicious site

For more information about the vulnerabilities, see the Vulnerability Information section.

For more information about this update, see Microsoft Knowledge Base Article 3049563.

Affected Software

The following software versions or editions are affected. Versions or editions that are not listed are either past their support life cycle or are not affected. To determine the support life cycle for your software version or edition, see Microsoft Support Lifecycle.

Affected Software 

^[1]This update is available via Windows Update.

Note Windows Technical Preview and Windows Server Technical Preview are affected. Customers running these operating systems are encouraged to apply the update, which is available via Windows Update. 

Update FAQ

For addressing CVE-2015-1684 and CVE-2015-1686, what updates apply to my system?
CVE-2015-1684 is a vulnerability in the VBScript engine and CVE-2015-1686 is a vulnerability in the JScript and VBScript engines. Although the attack vector is through Internet Explorer, the vulnerabilities are addressed by this update (3049563) only for systems running Internet Explorer 8, Internet Explorer 9, Internet Explorer 10, and Internet Explorer 11. For Internet Explorer 7 and earlier and for systems without Internet Explorer installed, the vulnerabilities are addressed by the update described in MS15-053.

The update that addresses CVE-2015-1684 and CVE-2015-1686 depends on the version of the JScript and VBScript scripting engines that are installed on your system. Consult the following table for update information.

Does this update contain any additional security-related changes to functionality?
In addition to the changes that are listed for the vulnerabilities described in this bulletin, this update includes defense-in-depth updates to help improve security-related features.

Severity Ratings and Vulnerability Identifiers

The following severity ratings assume the potential maximum impact of the vulnerability. For information regarding the likelihood, within 30 days of this security bulletin's release, of the exploitability of the vulnerability in relation to its severity rating and security impact, please see the Exploitability Index in the May bulletin summary.

Where specified in the Severity Ratings and Impact table, Critical, Important, and Moderate values indicate severity ratings. For more information, see Security Bulletin Severity Rating System. Refer to the following key for the abbreviations used in the table to indicate maximum impact:

^[1]Internet Explorer 7 installed on Windows Server 2003 is not affected by this vulnerability.

Vulnerability Information

VBScript ASLR Bypass - CVE-2015-1684

A security feature bypass exists when the VBScript engine fails to use the Address Space Layout Randomization (ASLR) security feature, allowing an attacker to more reliably predict the memory offsets of specific instructions in a given call stack. The security feature bypass by itself does not allow arbitrary code execution. However, an attacker could use the ASLR bypass in conjunction with another vulnerability, such as a remote code execution vulnerability, that could take advantage of the ASLR bypass to more reliably run arbitrary code on a target system.

In a web-browsing scenario, successful exploitation of an ASLR bypass requires that a user is logged on and running an affected version of Internet Explorer, and browses to a malicious website. Therefore, any systems where a web browser is used frequently, such as workstations or terminal servers, are at the most risk from ASLR bypasses. Servers could be at more risk if administrators allow users to browse and read email on servers. However, best practices strongly discourage allowing this.

The update addresses this ASLR bypass by helping to ensure that affected versions of VBScript properly implement the ASLR security feature. The following table contains links to the standard entry for each vulnerability in the Common Vulnerabilities and Exposures list:

Mitigating Factors

Microsoft has not identified any mitigating factors for this vulnerability.

Workarounds

The following workarounds may be helpful in your situation:

• Restrict access to VBScript.dll

  • For 32-bit systems, enter the following command at an administrative command prompt:

          takeown /f %windir%\system32\vbscript.dll   
          cacls %windir%\system32\vbscript.dll /E /P everyone:N          
  

  • For 64-bit systems, enter the following command at an administrative command prompt:

          takeown /f %windir%\syswow64\vbscript.dll   
          cacls %windir%\syswow64\vbscript.dll /E /P everyone:N         
  

  Impact of Workaround. Websites that use VBScript may not work properly.

  How to undo the workaround.

  • For 32-bit systems, enter the following command at an administrative command prompt:

          cacls %windir%\system32\vbscript.dll /E /R everyone          
  

  • For 64-bit systems, enter the following command at an administrative command prompt:

          cacls %windir%\syswow64\vbscript.dll /E /R everyone          
  

VBScript and JScript ASLR Bypass - CVE-2015-1686

A security feature bypass exists when the JScript and VBScript engines fail to use the Address Space Layout Randomization (ASLR) security feature, allowing an attacker to more reliably predict the memory offsets of specific instructions in a given call stack. The security feature bypass by itself does not allow arbitrary code execution. However, an attacker could use the ASLR bypass in conjunction with another vulnerability, such as a remote code execution vulnerability, to more reliably run arbitrary code on a target system.

In a web-browsing scenario, successful exploitation of an ASLR bypass requires that a user is logged on and running an affected version of Internet Explorer, and browses to a malicious site. Therefore, any systems where a web browser is used frequently, such as workstations or terminal servers, are at the most risk from ASLR bypasses. Servers could be at more risk if administrators allow users to browse and read email on servers. However, best practices strongly discourage allowing this.

The update addresses this ASLR bypasses by helping to ensure that affected versions of JScript and VBScript properly implement the ASLR security feature. The following table contains links to the standard entry for each vulnerability in the Common Vulnerabilities and Exposures list:

Mitigating Factors

Microsoft has not identified any mitigating factors for this vulnerability.

Workarounds

Microsoft has not identified any workarounds for this vulnerability.

Internet Explorer ASLR Bypass - CVE-2015-1685

A security feature bypass vulnerability exists when Internet Explorer fails to use the Address Space Layout Randomization (ASLR) security feature, allowing an attacker to more reliably predict the memory offsets of specific instructions in a given call stack. An attacker who successfully exploited this vulnerability could bypass the Address Space Layout Randomization (ASLR) security feature, which helps protect users from a broad class of vulnerabilities. The security feature bypass by itself does not allow arbitrary code execution. However, an attacker could use this ASLR bypass vulnerability in conjunction with another vulnerability, such as a remote code execution vulnerability, to more reliably run arbitrary code on a target system.

In a web-browsing scenario, successful exploitation of this vulnerability requires that a user is logged on and running an affected version of Internet Explorer, and browses to a malicious site. Therefore, any systems where a web browser is used frequently, such as workstations or terminal servers, are at the most risk from this vulnerability. Servers could be at more risk if administrators allow users to browse and read email on servers. However, best practices strongly discourage allowing this.

The update addresses the vulnerability by helping to ensure that affected versions of Internet Explorer properly implement the ASLR security feature. The following table contains links to the standard entry for each vulnerability in the Common Vulnerabilities and Exposures list:

Mitigating Factors

Microsoft has not identified any mitigating factors for this vulnerability.

Workarounds

Microsoft has not identified any workarounds for this vulnerability.

Multiple Elevation of Privilege Vulnerabilities

Elevation of privilege vulnerabilities exist when Internet Explorer does not properly validate permissions under specific conditions, potentially allowing script to be run with elevated privileges.

In a web-based attack scenario, an attacker could host a website that is used to attempt to exploit these vulnerabilities. In addition, compromised websites and websites that accept or host user-provided content could contain specially crafted content that could exploit these vulnerabilities. In all cases, however, an attacker would have no way to force users to view the attacker-controlled content. Instead, an attacker would have to convince users to take action. For example, an attacker could trick users into clicking a link that takes them to the attacker's site. An attacker who successfully exploited these vulnerabilities could elevate privileges in affected versions of Internet Explorer.

These vulnerabilities by themselves do not allow arbitrary code to be run. However, these vulnerabilities could be used in conjunction with another vulnerability (e.g., a remote code execution vulnerability) that could take advantage of the elevated privileges when running arbitrary code. For example, an attacker could exploit another vulnerability to run arbitrary code through Internet Explorer, but due to the context in which processes are launched by Internet Explorer, the code might be restricted to run at a low integrity level (very limited permissions). However, an attacker could, in turn, exploit these vulnerabilities to cause the arbitrary code to run at a medium integrity level (permissions of the current user).

The update addresses the vulnerabilities by adding additional permission validations to Internet Explorer. The following table contains links to the standard entry for each vulnerability in the Common Vulnerabilities and Exposures list:

Mitigating Factors

Microsoft has not identified any mitigating factors for these vulnerabilities.

Workarounds

Microsoft has not identified any workarounds for these vulnerabilities.

Internet Explorer Clipboard Information Disclosure Vulnerability - CVE-2015-1692

An information disclosure vulnerability exists when Internet Explorer does not properly restrict access to the clipboard of a user who visits a website. The vulnerability could allow data stored in the Windows clipboard to be accessed by a malicious site. An attacker could collect information from the clipboard of a user if that user visits the malicious site and performs a clipboard operation.

In a web-based attack scenario, an attacker could host a website that is used to attempt to exploit this vulnerability. In addition, compromised websites and websites 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 view the attacker-controlled content. Instead, an attacker would have to convince users to take action. For example, an attacker could trick users into clicking a link that takes them to the attacker's site. An attacker who successfully exploited this vulnerability could collect information from the clipboard if that user visits the malicious site and performs a clipboard operation.

The update addresses the vulnerability by restricting access to the information stored in a user’s clipboard. The following table contains links to the standard entry for each vulnerability in the Common Vulnerabilities and Exposures list:

Mitigating Factors

Microsoft has not identified any mitigating factors for this vulnerability.

Workarounds

The following workarounds may be helpful in your situation:

• Disable script access to the clipboard in Internet Explorer
  You can disable script access to the clipboard in Internet Explorer by modifying the Security settings

  To deny access to the clipboard, perform the following steps:

  1. On the Internet Explorer Tools menu, click Internet Options.
  2. In the Internet Options dialog box, click the Security tab.
  3. Click Internet to select the Internet zone and then click Custom Level
  4. In the Settings menu, scroll to Allow Programmatic clipboard access and click Disable.
  5. Click OK two times to exit the Internet Options dialog box.
      

• Impact of workaround. Web scripts will not be able to access the clipboard.

• How to undo the workaround.

  1. On the Internet Explorer Tools menu, click Internet Options.
  2. In the Internet Options dialog box, click the Security tab.
  3. Click Internet to select the Internet zone and then click Custom Level
  4. In the Settings menu, scroll to Allow Programmatic clipboard access and click Enable.
  5. Click OK two times to exit the Internet Options dialog box.  

• Disable script access to the clipboard in Group Policy

  1. Open the Group Policy Management Console (GPMC).

  2. In the Group Policy Management Editor, browse to the following setting:

     Computer Configuration -> Administrative Templates -> Windows Components -> Internet Explorer -> Internet Control Panel -> Security Page -> Internet Zone

  3. Right-click Allow cut, copy, or paste operations from the clipboard via script and then****click Edit.

  4. In the Allow paste operation via script dialog box click Disabled.

  5. Click OK and then restart the computer.  

  Impact of workaround. Web scripts will not be able to access the clipboard.

  How to undo the workaround.

  1. Open the Group Policy Management Console (GPMC).

  2. In the Group Policy Management Editor, browse to the following setting:

     Computer Configuration -> Administrative Templates -> Windows Components -> Internet Explorer -> Internet Control Panel -> Advanced Page -> Turn off encryption support

  3. Right-click Allow cut, copy, or paste operations from the clipboard via script and then****click Edit.

  4. In the Allow paste operation via script dialog box click Enabled.

  5. Click OK and then restart the computer.

FAQ

I am running Internet Explorer for Windows Server 2003, Windows Server 2008, Windows Server 2008 R2, Windows Server 2012, or Windows Server 2012 R2. Does this mitigate this vulnerability? 
Yes. By default, Internet Explorer on Windows Server 2003, Windows Server 2008, Windows Server 2008 R2, Windows Server 2012, and Windows Server 2012 R2 runs in a restricted mode that is known as Enhanced Security Configuration. Enhanced Security Configuration is a group of preconfigured settings in Internet Explorer that can reduce the likelihood of a user or administrator downloading and running specially crafted web content on a server. This is a mitigating factor for websites that you have not added to the Internet Explorer Trusted sites zone.

Multiple Memory Corruption Vulnerabilities in Internet Explorer

Remote code execution vulnerabilities exist when Internet Explorer improperly accesses objects in memory. These vulnerabilities could corrupt memory in such a way that an attacker could execute arbitrary code in the context of the current user.

An attacker could host a specially crafted website that is designed to exploit these vulnerabilities through Internet Explorer, and then convince a user to view the website. The attacker could also take advantage of compromised websites and websites that accept or host user-provided content or advertisements by adding specially crafted content that could exploit these vulnerabilities. In all cases, however, an attacker would have no way to force users to view the attacker-controlled content. Instead, an attacker would have to convince users to take action, typically by getting them to click a link in an instant messenger or email message that takes users to the attacker's website, or by getting them to open an attachment sent through email.

An attacker who successfully exploited these vulnerabilities could gain the same user rights as the current user. If the current user is logged on with administrative user rights, an attacker who successfully exploited these vulnerabilities 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. Systems where Internet Explorer is used frequently, such as workstations or terminal servers, are at the most risk from these vulnerabilities.

The update addresses the vulnerabilities by modifying how Internet Explorer handles objects in memory. The following table contains links to the standard entry for each vulnerability in the Common Vulnerabilities and Exposures list:

Mitigating Factors

Microsoft has not identified any mitigating factors for these vulnerabilities.

Workarounds

Microsoft has not identified any workarounds for these vulnerabilities.

FAQ

I am running Internet Explorer on Windows Server 2003, Windows Server 2008, Windows Server 2008 R2, Windows Server 2012, or Windows Server 2012 R2. Does this mitigate these vulnerabilities? 
Yes. By default, Internet Explorer on Windows Server 2003, Windows Server 2008, Windows Server 2008 R2, Windows Server 2012, and Windows Server 2012 R2 runs in a restricted mode that is known as Enhanced Security Configuration. Enhanced Security Configuration is a group of preconfigured settings in Internet Explorer that can reduce the likelihood of a user or administrator downloading and running specially crafted web content on a server. This is a mitigating factor for websites that you have not added to the Internet Explorer Trusted sites zone.

Can EMET help mitigate attacks that attempt to exploit these vulnerabilities? 
Yes. The Enhanced Mitigation Experience Toolkit (EMET) enables users to manage security mitigation technologies that help make it more difficult for attackers to exploit memory corruption vulnerabilities in a given piece of software. EMET can help mitigate attacks that attempt to exploit these vulnerabilities in Internet Explorer on systems where EMET is installed and configured to work with Internet Explorer.

For more information about EMET, see the Enhanced Mitigation Experience Toolkit.

Security Update Deployment

For Security Update Deployment information see the Microsoft Knowledge Base article referenced in the Executive Summary.

Acknowledgments

Microsoft recognizes the efforts of those in the security community who help us protect customers through coordinated vulnerability disclosure. See Acknowledgments for more information.

Disclaimer

The information provided in the Microsoft Knowledge Base 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.

Revisions

• V1.0 (May 12, 2015): Bulletin published.

Page generated 2015-05-06 13:56Z-07:00.