MS16-075 - Important: Security Update for Windows SMB Server (3164038) - Version: 1.0

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Microsoft Security Bulletin MS16-075 - Important

Security Update for Windows SMB Server (3164038)

Published: June 14, 2016

Version: 1.0

This security update resolves a vulnerability in Microsoft Windows. The vulnerability could allow elevation of privilege if an attacker logs on to the system and runs a specially crafted application.

This security update is rated Important for all supported releases of Microsoft Windows. For more information, see the Affected Software and Vulnerability Severity Ratings section.

The security update addresses the vulnerability by correcting how Windows Server Message Block (SMB) Server handles credential forwarding requests. For more information about the vulnerability, see the Vulnerability Information section.

For more information about this update, see Microsoft Knowledge Base Article 3164038.

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.

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.

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

[2]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 update is available via the Windows Update Catalog.

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*The Updates Replaced column shows only the latest update in any chain of superseded updates.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

Why is security update 3161561 in this bulletin also denoted in MS16-076? 
Security update 3161561 is also denoted in MS16-076 for supported releases of Windows Server 2008, Windows Server 2008 R2, Windows Server 2012, and Windows Server 2012 R2, due to the way fixes for vulnerabilities affecting particular products are consolidated. Because bulletins are broken out by the vulnerabilities being addressed, not by the update package being released, it is possible for separate bulletins, each addressing distinctly different vulnerabilities, to list the same update package as the vehicle for providing their respective fixes. This is frequently the case with cumulative updates for products, such as Internet Explorer or Silverlight, where singular security updates address different security vulnerabilities in separate bulletins.

Note Users do not need to install identical security updates that ship with multiple bulletins more than once.

Windows SMB Server Elevation of Privilege Vulnerability - CVE-2016-3225

An elevation of privilege vulnerability exists in the Microsoft Server Message Block (SMB) when an attacker forwards an authentication request intended for another service running on the same machine. An attacker who successfully exploited this vulnerability could execute arbitrary code with elevated permissions.

To exploit the vulnerability, an attacker would first have to log on to the system. An attacker could then run a specially crafted application that could exploit the vulnerability and take control of an affected system. The update addresses the vulnerability by correcting how Windows Server Message Block (SMB) Server handles credential forwarding requests.

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

Vulnerability title	CVE number	Publicly disclosed	Exploited
Windows SMB Server Elevation of Privilege Vulnerability	CVE-2016-3225	Yes	No

Mitigating Factors

The following mitigating factors may be helpful in your situation:

• An attacker must have valid logon credentials and be able to log on locally to exploit this vulnerability.

Workarounds

The following workarounds may be helpful in your situation:

• Enable Extended Protection for Authentication (EPA) for SMB server
  • For customers running Windows Vista and Windows Server 2008

    You must have update 968389 installed on both client and server computers. To download the update, see Microsoft Knowledge Base Article 968389. You must also have update 2345886 installed on both client and server computers. If the update is not already installed on your system, you can download it from the Microsoft Update Catalog. After you install update 2345886, the EPA security feature is off by default as it may cause some application compatibility concerns. To enable EPA for SMB clients and servers, see the References section of Microsoft Knowledge Base Article 2345886.

  • For customers running Windows 7 and Windows Server 2008 R2

    You must have update 2345886 installed on both client and server computers. If the update is not already installed on your system, you can download it from the Microsoft Update Catalog. After you install the update, the EPA security feature is off by default as it may cause some application compatibility concerns. To enable EPA for SMB clients and servers, see the References section of Microsoft Knowledge Base Article 2345886. Note that the instructions in this article also apply to later releases of Microsoft Windows.

  • For customers running Windows 8 and later versions of Windows

    The EPA security feature is built into the operating system, but is off by default as it may cause some application compatibility concerns. To enable EPA for SMB clients and servers, see the References section of Microsoft Knowledge Base Article 2345886. Note that the instructions in this article also apply to later releases of Microsoft Windows.

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

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

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.

• V1.0 (June 14, 2016): Bulletin published.

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