Microsoft Security Bulletin MS16-094 - Important

Security Update for Secure Boot (3177404)

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

Version: 1.1

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.

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

Updates Replaced*

Windows 8.1

Windows 8.1 for 32-bit Systems
(3172727)

Important 
Security Feature Bypass

None

Windows 8.1 for x64-based Systems
(3172727)

Important 
Security Feature Bypass

None

Windows Server 2012 and Windows Server 2012 R2

Windows Server 2012
(3172727)

Important 
Security Feature Bypass

None

Windows Server 2012 R2
(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 [2]
(3163912)

Important 
Security Feature Bypass

3163017

Windows 10 for x64-based Systems [2]
(3163912)

Important 
Security Feature Bypass

3163017

Windows 10 Version 1511 for 32-bit Systems [2]
(3172985)

Important 
Security Feature Bypass

3163018

Windows 10 Version 1511 for x64-based Systems [2]
(3172985)

Important 
Security Feature Bypass

3163018

Server Core installation option

Windows Server 2012 (Server Core installation)
(3172727)

Important 
Security Feature Bypass

None

Windows Server 2012 R2 (Server Core installation)
(3172727)

Important 
Security Feature Bypass

None

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

[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).

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.

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 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 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: <OR OS volume letter>  -tpmandpin
      
    9. When the command asks for a PIN, enter a 4- or 6-digit PIN.
    10. Restart the system.

    Impact of workaround. 

    The user will be required to enter the PIN every time the computer restarts.

    How to undo the workaround

    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 Allow TPM and Allow startup PIN with TPM.
    6. Click Apply and exit the Local Group Policy Editor.
    7. Restart the system.
  • Disable Secure Boot integrity protection of BitLocker

    To disable Secure Boot, you must follow each of the steps in order.

    1. Disable BitLocker
      1. Open Control Panel, then click BitLocker Drive Encryption.
      2. Click Turn off BitLocker
      3. In the BitLocker Drive Encryption dialog box, click Turn off BitLocker.
      4. Exit Control Panel.
    2. Disable Secure Boot
      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. Double-click Allow Secure Boot for integrity validation.
      4. In the dialog box that appears, click Disabled.
      5. Click Apply and exit the Local Group Policy Editor.
    3. Re-enable BitLocker
      1. Open Control Panel, then click BitLocker Drive Encryption.
      2. Click Turn on BitLocker
      3. In the BitLocker Drive Encryption dialog box, click Turn on BitLocker.
      4. Exit Control Panel.

    Impact of workaround. 

    Disabling Secure Boot may cause systems to enter BitLocker recovery more often when you update firmware versions or BCD settings.


    How to undo the workaround. 

    1. Disable BitLocker
      1. Open Control Panel, then click BitLocker Drive Encryption.
      2. Click Turn off BitLocker
      3. In the BitLocker Drive Encryption dialog box, click Turn off BitLocker.
      4. Exit Control Panel.
    2. Enable Secure Boot
      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. Double-click Allow Secure Boot for integrity validation.
      4. In the dialog box that appears, click Enabled.
      5. Click Apply and exit the Local Group Policy Editor.
    3. Re-enable BitLocker
      1. Open Control Panel, then click BitLocker Drive Encryption.
      2. Click Turn on BitLocker
      3. In the BitLocker Drive Encryption dialog box, click Turn on BitLocker.
      4. Exit Control Panel.

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 (July 12, 2016): Bulletin published.
  • V1.1 (July 18, 2016): Bulletin revised to add an Update FAQ to inform customers running Windows Server 2012 that they do not need to install the 3170377 and 3172727 updates in a particular order.
Page generated 2016-08-18 09:19-07:00.
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