Microsoft Security Bulletin MS15-065 - Critical

• 10/11/2017
• 30 minutes to read
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Security Update for Internet Explorer (3076321)

Published: July 22, 2015

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 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, VBScript, and JScript handle objects in memory
• Helping to ensure that affected versions of Internet Explorer properly implement the CFG security feature
• Preventing the XSS filter in Internet Explorer from incorrectly disabling HTML attributes
• Adding additional permission validations to Internet Explorer
• Helping to ensure that affected versions of Internet Explorer properly implement the ASLR security feature
• Helping to ensure cross-domain policies are properly enforced in Internet Explorer
• Helping to restrict what information is returned to external stylesheets
• Helping to ensure that file paths are properly validated before returning file data to the user
• Helping to ensure that requests for module resources are properly validated in Internet Explorer

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

For more information about this update, see Microsoft Knowledge Base Article 3065822.

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 

*The Updates Replaced column shows only the latest update in a 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 on the Package Details tab).

Update FAQ

I am running Internet Explorer 7, Internet Explorer 8, or Internet Explorer 9. Are there additional updates I should be aware of? 
Yes. For Internet Explorer 7, Internet Explorer 8, and Internet Explorer 9, update 3074886 is bundled with update 3065822. For more information about this update, please see Microsoft Knowledge Base Article 3074886.

Note For Windows Update, Windows Server Update Services (WSUS), or Microsoft Update Catalog customers:

Update 3074886 is installed automatically and transparently together with security update 3065822. Update 3074886 will appear separately from security update 3065822 in the list of installed updates when viewed in the Add Remove Programs or the Programs and Features item in Control Panel.

Note For Download Center customers:

If you download and install updates manually, you must first install update 3065822 before installing update 3074886. Failure to follow the install order or failure to install 3074886 after installing 3065822 can lead to degraded functionality.

I am running Internet Explorer 10 or Internet Explorer 11. Are there any other additional updates I should be aware of?
Yes. Systems running Internet Explorer 10 or Internet Explorer 11 will not be fully protected until you have installed both security update 3065822 and security update 3075516. In addition, update 3074886 is also bundled with update 3065822.

Note For Windows Update, Windows Server Update Services (WSUS), or Microsoft Update Catalog customers:

Security update 3075516 and update 3074886 are installed automatically and transparently together with security update 3065822 on applicable systems. Updates 3075516 and 3074886 will appear separately from update 3065822 in the list of installed updates when viewed in the Add or Remove Programs or the Programs and Features item in Control Panel.

Note For Download Center customers:

If you download and install updates manually, you must first install security update 3065822 before installing update 3075516 or update 3074886. Failure to follow the install order or failure to install 3075516 and 3074886 after installing 3065822 can lead to degraded functionality.

For addressing CVE-2015-2372, what updates apply to my system? 
CVE-2015-2372 is a vulnerability in the VBScript engine. Although the attack vector is through Internet Explorer, the vulnerability is addressed by this update (3065822) 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 vulnerability is addressed by the update described in MS15-066.

The update that addresses CVE-2015-2372 depends on the version of the VBScript scripting engine that is installed on your system. Consult the following table for update information.

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 July 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

VBScript Memory Corruption Vulnerability - CVE-2015-2372

A remote code execution vulnerability exists in the way that the VBScript engine, when rendered in Internet Explorer, handles objects in memory. In a web-based attack scenario, an attacker could host a specially crafted website that is designed to exploit this vulnerability through Internet Explorer and then convince a user to view the website. An attacker could also embed an ActiveX control marked "safe for initialization" in an application or Microsoft Office document that hosts the IE rendering engine. The attacker could also take advantage of compromised websites and websites that accept or host user-provided content or advertisements. These websites could contain specially crafted content that could exploit this vulnerability.

An attacker who successfully exploited this vulnerability 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 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. The update addresses the vulnerability by modifying how the VBScript scripting engine 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
```
    

-   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
```

Internet Explorer XSS Filter Bypass Vulnerability – CVE-2015-2398

An XSS filter bypass vulnerability exists in the way that Internet Explorer disables an HTML attribute in otherwise appropriately filtered HTTP response data. The vulnerability could allow initially disabled scripts to run in the wrong security context, leading to information disclosure.

An attacker could post on a website specially crafted content that is designed to exploit this vulnerability. The attacker would then have to convince the user to view the content on the affected website. If the user then browses to the website, the XSS filter disables HTML attributes in the specially crafted content, creating a condition that could allow malicious script to run in the wrong security context, leading to information disclosure.

An attacker who successfully exploited this vulnerability could cause script code to run on another user's system in the guise of a third-party website. Such script code would run inside the browser when visiting the third-party website, and could take any action on the user's system that the third-party website was permitted to take. The vulnerability could only be exploited if the user clicked a hypertext link, either in an HTML email or if the user visited an attacker's website or a website containing content that is under the attacker’s control. Any systems where Internet Explorer is used frequently, such as workstations and terminal servers, are at the most risk from this vulnerability.

The update addresses the vulnerability by preventing the XSS filter in Internet Explorer from incorrectly disabling HTML attributes.

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