Microsoft Security Bulletin MS15-126 - Critical

Cumulative Security Update for JScript and VBScript to Address Remote Code Execution (3116178)

Published: December 8, 2015 | Updated: May 25, 2016

Version: 1.1

Executive Summary

This security update resolves vulnerabilities in the VBScript scripting engine in Microsoft Windows. The more severe of the vulnerabilities could allow remote code execution if an attacker hosts a specially crafted website that is designed to exploit the vulnerabilities through Internet Explorer (or leverages a compromised website or a website that accepts or hosts user-provided content or advertisements) and then convinces 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 uses the Internet Explorer rendering engine to direct the user to the specially crafted website.

An attacker who successfully exploited the vulnerabilities could gain the same user rights as the current user and, 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.

This security update is rated Critical for affected versions of the VBScript scripting engine on supported editions of Windows Vista, Windows Server 2008, and Server Core installations of Windows Server 2008 R2. For more information, see the AffectedSoftware section.

The update addresses the vulnerabilities by modifying how the VBScript scripting engine handle objects in memory. For more information about the vulnerabilities, see the VulnerabilityInformation section.

For more information about this update, see Microsoft Knowledge Base Article 3116178.

Affected Software

The following versions of VBScript are affected by the vulnerability discussed in this bulletin. Earlier versions or editions that are not listed are either past their support life cycle or are not affected. The following affected software apply to systems with Internet Explorer 7 or earlier installed and to systems without Internet Explorer installed. Customers with systems running Internet Explorer 8 or later should apply Internet Explorer Cumulative Update 3104002 (MS15-124), which also addresses the vulnerability discussed in this bulletin.

Affected Software 

*The Updates Replaced column shows only the latest update in any chain of superseded updates.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

Why do I see both JScript.dll and VBScript.dll in the packages for this cumulative security update?
This security update ships as a cumulative update for the JScript and VBScript scripting engines. While both engines are included in this release, the components affected by the security fixes covered by this bulletin are listed above in the section AffectedSoftware.

How do I determine which versions of JScript and VBScript scripting engines are installed on my system?
The JScript and VBScript scripting engines are installed with supported releases of Microsoft Windows. In addition, installing a newer version of Internet Explorer on a system can change the version of the JScript and VBScript scripting engine that are installed.

To determine which versions of the JScript or VBScript scripting engines are installed on your system, perform the following steps:

1. Open Windows Explorer.
2. Navigate to the %systemroot%\system32 directory.
3. For VBScript, right-click vbscript.dll, select Properties, and then click the Details tab.
4. For JScript, right-click jscript.dll, select Properties, and then click the Details tab.

The version number is listed in the File Version field. If your file version starts with 5.8, for example 5.8.7600.16385, then VBScript 5.8 is installed on your system.

Once I know the version of the JScript or VBScript scripting engine installed on my system, where do I get the update?
The affected software in this bulletin apply to systems without Internet Explorer installed and to systems with Internet Explorer 7 or earlier versions installed. Customers with systems running Internet Explorer 8 or later should apply the Internet Explorer Cumulative Update (MS15-124), which also addresses the vulnerabilities discussed in this bulletin.

The following table summarizes which bulletin provides the update by version of JScript and VBScript, and Internet Explorer.

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 December bulletin summary.

Vulnerability Information

Scripting Engine Information Disclosure Vulnerability - CVE-2015-6135

An information disclosure vulnerability exists when VBScript improperly discloses the contents of its memory, which could provide an attacker with information to further compromise the user’s computer or data.

To exploit the vulnerability, an attacker must know the memory address of where the object was created. The update addresses the vulnerability by changing the way certain functions handle objects in memory.

Microsoft received information about this vulnerability through coordinated vulnerability disclosure. When this security bulletin was originally issued, Microsoft had not received any information to indicate that the vulnerability had been publicly used to attack customers.

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
    

Scripting Engine Memory Corruption Vulnerability - CVE-2015-6136

A remote code execution vulnerability exists in the way that the VBScript engine renders, when handling objects in memory in Internet Explorer. In a web-based attack scenario, an attacker could host a specially crafted website that is designed to exploit the 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 the vulnerability.

An attacker who successfully exploited the 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 the vulnerability 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. The update addresses the vulnerability by modifying how the VBScript scripting engine handle objects in memory.

Microsoft received information about this vulnerability through coordinated vulnerability disclosure. When this security bulletin was originally issued, Microsoft had not received any information to indicate that the vulnerability had been publicly used to attack customers.

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
    

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 (December 8, 2015): Bulletin published.
• V1.1 (May 25, 2016): Removed redundant rows from the Vulnerability Severity Rating and Maximum Security Impact by Affected Software table, and added the applicable update numbers for clarity. This is an informational change only.

Page generated 2016-05-25 12:57-07:00.