Microsoft Security Bulletin MS16-112 - Important

Security Update for Windows Lock Screen (3178469)

Published: September 13, 2016

Version: 1.0

Executive Summary

This security update resolves a vulnerability in Microsoft Windows. The vulnerability could allow elevation of privilege if Windows improperly allows web content to load from the Windows lock screen.

This security update is rated Important for all supported editions of Windows 8.1, Windows RT 8.1, 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 correcting the behavior of the Windows lock screen to prevent unintended web content from loading. For more information about the vulnerabilities, see the Vulnerability Information section.

For more information about this update, see Microsoft Knowledge Base Article 3178469.

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 September bulletin summary.

Operating System Windows Lock Screen Elevation of Privilege Vulnerability - CVE-2016-3302 Updates Replaced*
Windows 8.1
Windows 8.1 for 32-bit Systems
(3178539)
Important
Elevation of Privilege
None
Windows 8.1 for x64-based Systems
(3178539)
Important
Elevation of Privilege
None
Windows Server 2012 R2
Windows Server 2012 R2
(3178539)
Important
Elevation of Privilege
None
Windows RT 8.1
Windows RT 8.1[1] (3178539) Important
Elevation of Privilege
None
Windows 10
Windows 10 for 32-bit Systems[2] (3185611) Important
Elevation of Privilege
3176492
Windows 10 for x64-based Systems[2] (3185611) Important
Elevation of Privilege
3176492
Windows 10 Version 1511 for 32-bit Systems[2] (3185614) Important
Elevation of Privilege
3176493
Windows 10 Version 1511 for x64-based Systems[2] (3185614) Important
Elevation of Privilege
3176493
Windows 10 Version 1607 for 32-bit Systems[2] (3189866) Important
Elevation of Privilege
3176495
Windows 10 Version 1607 for x64-based Systems[2] (3189866) Important
Elevation of Privilege
3176495
Server Core installation option
Windows Server 2012 R2 (Server Core installation)
(3178539)
Important
Elevation of Privilege
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 vulnerabilities discussed in this bulletin affect Windows Server 2016 Technical Preview 5. To be protected from the vulnerabilities, Microsoft recommends that customers running this operating system apply the current update, which is available from 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).

Vulnerability Information

Windows Lock Screen Elevation of Privilege Vulnerability – CVE-2016-3302

An elevation of privilege vulnerability exists when Windows improperly allows web content to load from the Windows lock screen. To exploit the vulnerability, an attacker with physical access to a user’s computer could either connect to a maliciously configured WiFi hotspot or insert a mobile broadband adaptor in the user’s computer. An attacker who successfully exploited the vulnerability could potentially execute code on a user's locked computer.

However, the attacker would have no way to either force a user to connect to the hotspot or control the default browser selection on the user’s computer. The security update addresses the vulnerability by correcting the behavior of the Windows lock screen to prevent unintended web content from loading.

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 Lock Screen Elevation of Privilege Vulnerability CVE-2016-3302 No No

Mitigating Factors

Microsoft has not identified any mitigating factors for this vulnerability.

Workarounds

Microsoft has not identified any workarounds for this vulnerability.

Security Update Deployment

For Security Update Deployment information, see the Microsoft Knowledge Base article referenced here 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 (September 13, 2016): Bulletin published.

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