Microsoft Security Bulletin MS16-094 - Important

Security Update for Secure Boot (3177404)

Published: July 12, 2016 | Updated: July 18, 2016

Version: 1.1

Executive Summary

This security update resolves a vulnerability in Microsoft Windows. The vulnerability could allow Secure Boot security features to be bypassed if an attacker installs an affected policy on a target device. An attacker must have either administrative privileges or physical access to install a policy and bypass Secure Boot.

This security update is rated Important for all supported editions of Windows 8.1, Windows RT 8.1, Windows Server 2012, Windows Server 2012 R2, and Windows 10. For more information, see the Affected Software and Vulnerability Severity Ratings section.

The security update addresses the vulnerability by blacklisting affected policies. For more information about the vulnerabilities see the Vulnerability Information section.

For more information about this update, see Microsoft Knowledge Base Article 3177404.

Affected Software and Vulnerability Severity Ratings

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 July bulletin summary.

**Vulnerability Severity Rating and Maximum Security Impact by Affected Software**
**Affected Software** [**Secure Boot Security Feature Bypass - CVE-2016-3287**](http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=cve-2016-3287) **Updates Replaced**\*
**Windows 8.1**
[Windows 8.1 for 32-bit Systems](https://www.microsoft.com/download/details.aspx?familyid=a16c58cf-4e79-4e51-b39b-50ff623c5ff9) (3172727) **Important**  Security Feature Bypass None
[Windows 8.1 for x64-based Systems](https://www.microsoft.com/download/details.aspx?familyid=0afae908-718e-4f83-9b8b-f276aa12ecaf) (3172727) **Important**  Security Feature Bypass None
**Windows Server 2012 and Windows Server 2012 R2**
[Windows Server 2012](https://www.microsoft.com/download/details.aspx?familyid=ef857803-9aa0-4284-9e34-0c0bf6d1f354) (3172727) **Important**  Security Feature Bypass None
[Windows Server 2012 R2](https://www.microsoft.com/download/details.aspx?familyid=ef357a04-dd1e-4c34-bfde-c4445f3a5379) (3172727) **Important**  Security Feature Bypass None
**Windows RT 8.1**
Windows RT 8.1[1] (3172727) **Important**  Security Feature Bypass None
**Windows 10**
[Windows 10 for 32-bit Systems](https://support.microsoft.com/kb/3163912)[2] (3163912) **Important**  Security Feature Bypass [3163017](https://support.microsoft.com/kb/3163017)
[Windows 10 for x64-based Systems](https://support.microsoft.com/kb/3163912)[2] (3163912) **Important**  Security Feature Bypass [3163017](https://support.microsoft.com/kb/3163017)
[Windows 10 Version 1511 for 32-bit Systems](https://support.microsoft.com/kb/3172985)[2] (3172985) **Important**  Security Feature Bypass [3163018](https://support.microsoft.com/kb/3163018)
[Windows 10 Version 1511 for x64-based Systems](https://support.microsoft.com/kb/3172985)[2] (3172985) **Important**  Security Feature Bypass [3163018](https://support.microsoft.com/kb/3163018)
**Server Core installation option**
[Windows Server 2012](https://www.microsoft.com/download/details.aspx?familyid=ef857803-9aa0-4284-9e34-0c0bf6d1f354) (Server Core installation) (3172727) **Important**  Security Feature Bypass None
[Windows Server 2012 R2](https://www.microsoft.com/download/details.aspx?familyid=ef357a04-dd1e-4c34-bfde-c4445f3a5379) (Server Core installation) (3172727) **Important**  Security Feature Bypass None
[1]This update is only available via [Windows Update](http://go.microsoft.com/fwlink/?linkid=21130).

[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 updates are available via the Microsoft Update Catalog.

Note The vulnerability discussed in this bulletin affects Windows Server 2016 Technical Preview 4 and Windows Server 2016 Technical Preview 5. An update is available for Windows Server 2016 Technical Preview 5 via Windows Update. However, no update is available for Windows Server 2016 Technical Preview 4. To be protected from the vulnerability, Microsoft recommends that customers running Windows Server 2016 Technical Preview 4 upgrade to Windows Server 2016 Technical Preview 5.

*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

I am running Windows Server 2012. Do I need to install the 3170377 and 3172727 updates in a particular order?
No. The 3170377 and 3172727 updates both contain the same components and can be installed in any order. Installing one and then the other without a system restart in between is allowed; however, if you install the 3172727 update first and then restart the system, subsequent attempts to install the 3170377 update will display the message, “The update is not applicable to your computer." This is because the 3172727 update supersedes the 3170377 update by design.

Vulnerability Information

Secure Boot Security Feature Bypass Vulnerability – CVE-2016-3287

A security feature bypass vulnerability exists when Windows Secure Boot improperly applies an affected policy. An attacker who successfully exploited this vulnerability could disable code integrity checks, allowing test-signed executables and drivers to be loaded on a target device. In addition, an attacker could bypass the Secure Boot Integrity Validation for BitLocker and the Device Encryption security features.

To exploit the vulnerability, an attacker must either gain administrative privileges or physical access to a target device to install an affected policy. The security update addresses the vulnerability by blacklisting affected policies.

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
Secure Boot Security Feature Bypass Vulnerability CVE-2016-3287 Yes No
### Mitigating Factors The following [mitigating factors](https://technet.microsoft.com/library/security/dn848375.aspx) may be helpful in your situation: - To exploit the vulnerability, an attacker must have either administrative privileges or physical access to the target device. ### Workarounds The following [workarounds](https://technet.microsoft.com/library/security/dn848375.aspx) may be helpful in your situation: - **Configure BitLocker to use Trusted Platform Module (TPM)+PIN protection** To enable TPM and PIN protector, enable the enhanced protection group policy as follows: 1. Click **Start**, click **Run**, type **gpedit.msc**, and then click **OK** to open the Local Group Policy Editor. 2. Under **Local Computer Policy**, navigate to Administrative Templates>Windows Components>BitLocker Drive Encryption>Operating Systems Drives. 3. In the right-hand pane, double-click **Require additional authentication at startup**. 4. In the dialog box that appears, click **Enabled**. 5. Under **Options**, select **Require TPM** and **Require startup PIN with TPM**. 6. Click **Apply** and exit the Local Group Policy Editor. 7. Open the command prompt with Administrator privileges. 8. Enter the following command: ``` manage-bde -protectors -add c: