Microsoft Security Bulletin MS16-063 - Critical

• 10/11/2017
• 15 minutes to read
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Cumulative Security Update for Internet Explorer (3163649)

Published: June 14, 2016 | Updated: June 22, 2016

Version: 1.1

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 the vulnerabilities could gain the same user rights as the current user. If the current user is logged on with administrative user rights, an attacker could take control of an affected system. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights.

This security update is rated Critical for Internet Explorer 9 (IE 9), and Internet Explorer 11 (IE 11) on affected Windows clients, and Moderate for 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 update addresses the vulnerabilities by:

• Modifying how Internet Explorer handles objects in memory
• Modifying how the JScript and VBScript scripting engines handle objects in memory
• Fixing how the Internet Explorer XSS Filter validates JavaScript
• Correcting how Windows handles proxy discovery

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

For more information about this update, see Microsoft Knowledge Base Article 3163649.

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.

^[2]This update is available via Windows Update.

^[3]Windows 10 updates are cumulative. The monthly security release includes all security fixes for vulnerabilities that affect Windows 10, in addition to non-security updates. The updates are available via the Microsoft Update Catalog.

Note Windows Server 2016 Technical Preview 5 is affected. Customers running this operating system are encouraged to apply the update, which is available via Windows Update.

*The Updates Replaced column shows only the latest update in any chain of superseded updates. For a comprehensive list of updates replaced, go to the Microsoft Update Catalog, search for the update KB number, and then view update details (updates replaced information is provided on the Package Details tab).

Update FAQ

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.

For my particular system and Internet Explorer configuration, which update addresses the vulnerabilities discussed in CVE-2016-3205, CVE-2016-3206, and CVE-2016-3207?
CVE-2016-3205, CVE-2016-3206, and CVE-2016-3207 are vulnerabilities in the VBScript engine. Although the attack vector is through Internet Explorer, the vulnerability is addressed by the updates released in this bulletin (MS16-063) for systems running Internet Explorer 9, Internet Explorer 10, and Internet Explorer 11. For Internet Explorer 7 and earlier, the vulnerabilities are addressed by the updates described in MS16-069.

Are there any further steps I need to carry out to be protected from CVE-2016-3213 described in this bulletin?
Yes. It is important to note that the security update described in this bulletin for CVE-2016-3213 does not fully protect your system. You must also install the update in MS16-077 to be fully protected from this vulnerability.

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 June 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:

Vulnerability Information

Microsoft Internet Explorer Memory Corruption Vulnerabilities

Remote code execution vulnerabilities exist when Internet Explorer improperly accesses objects in memory. The vulnerabilities could corrupt memory in such a way that an attacker could execute arbitrary code in the context of the current user. An attacker who successfully exploited the vulnerabilities could gain the same user rights as the current user. If the current user is logged on with administrative user rights, the attacker could take control of an affected system. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights.

An attacker could host a specially crafted website that is designed to exploit the vulnerabilities through Internet Explorer, and then convince a user to view the website. The attacker could also take advantage of compromised websites, or websites that accept or host user-provided content or advertisements, by adding specially crafted content that could exploit the 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 an enticement in an email or Instant Messenger message, or by getting them to open an attachment sent through email. 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:

    ```
        takeown /f %windir%\system32\vbscript.dll   
        cacls %windir%\system32\vbscript.dll /E /P everyone:N  
        cacls %windir%\system32\jscript.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  
        cacls %windir%\syswow64\jscript.dll /E /P everyone:N
    ```

**Impact of Workaround.** Websites that use VBScript or JScript 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  
        cacls %windir%\system32\jscript.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  
        cacls %windir%\syswow64\jscript.dll /E /R everyone
    ```

Internet Explorer XSS Filter Vulnerability - CVE-2016-3212

A remote code execution vulnerability exists when the Internet Explorer XSS Filter does not properly validate JavaScript under specific conditions. An attacker who exploited the vulnerability could run arbitrary code with medium-integrity level privileges (the permissions of the current user).

In a web-based attack scenario, an attacker could host a website in an 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 the vulnerability.

However, in all cases 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 the user to the attacker's site. The update addresses the vulnerability by fixing how the Internet Explorer XSS Filter validates JavaScript.

The following table contains links to the standard entry for each vulnerability in the Common Vulnerabilities and Exposures list: