MS16-077: Description of the security update for WPAD: June 14, 2016

Summary

This security update resolves vulnerabilities in Microsoft Windows. The vulnerabilities could allow elevation of privilege if the Web Proxy Auto Discovery (WPAD) protocol falls back to a vulnerable proxy discovery process on a target system.

To learn more about the vulnerability, see Microsoft Security Bulletin MS16-077.

More Information

Important

• All future security and non-security updates for Windows RT 8.1, Windows 8.1, and Windows Server 2012 R2 require update 2919355 to be installed. We recommend that you install update 2919355 on your Windows RT 8.1-based, Windows 8.1-based, or Windows Server 2012 R2-based computer so that you receive future updates.
• If you install a language pack after you install this update, you must reinstall this update. Therefore, we recommend that you install any language packs that you need before you install this update. For more information, see Add language packs to Windows.

Behavior changes after installation

After you install this security update, the following changes are applied:

• NETBIOS communication outside of the local subnet is hardened. Therefore, by default, some features that depend on NETBIOS (such as SMB over NETBIOS) will not work outside the local subnet. To change this new default behavior, create the following registry entry:SUBKEY: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\NetBT\Parameters
  Value Name: AllowNBToInternet
  Type: Dword
  Value: 1
  Default value of the flag: 0
• By default, WPAD resolution for auto proxy detection will not use NETBIOS. Therefore, if proxy detection depends on NETBIOS alone for WPAD resolution, it may fail. We recommend that you use the DHCP option or DNS for WPAD resolution instead of NETBIOS. To change this new default behavior, create the following registry entry.

Note This registry entry only applies for Windows 8.1 and earlier versions of Windows.
SUBKEY: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\WinHttp
Value Name: AllowOnlyDNSQueryForWPAD
Type: DWORD
Value: 0
Default value of the flag: 1

• The default behavior of PAC file download is changed so that the client’s domain credentials are not automatically sent in response to an NTLM or Negotiate Authentication challenge when WinHTTP requests the PAC file. This occurs regardless of the value of the fAutoLogonIfChallenged flag that is specified in WINHTTP_AUTOPROXY_OPTIONS. To change this new default behavior, create the following registry entry:

Note This registry entry only applies for Windows 8.1 and earlier versions of Windows.
SUBKEY: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\WinHttp
Value Name: AutoProxyAutoLogonIfChallenged
Type: DWORD
Value: 1
Default value of the flag: 0

How to obtain and install the update

Method 1: Windows Update

This update is available through Windows Update. When you turn on automatic updating, this update will be downloaded and installed automatically. For more information about how to turn on automatic updating, see
Get security updates automatically.

Note For Windows RT 8.1, this update is available through Windows Update only.

Method 2: Microsoft Download Center

You can obtain the stand-alone update package through the Microsoft Download Center. Follow the installation instructions on the download page to install the update.

Click the download link in Microsoft Security Bulletin MS16-077 that corresponds to the version of Windows that you are running.

More Information

How to obtain help and support for this security update

Help for installing updates: Support for Microsoft Update

Security solutions for IT professionals: TechNet Security Troubleshooting and Support

Help for protecting your Windows-based computer from viruses and malware: Virus Solution and Security Center

Local support according to your country: International Support

File Information

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File hash information

File name	SHA1 hash	SHA256 hash
Windows8.1-KB3161949-x86.msu	A15B1E6C4E2D8C061C13AD6697340030D11300F9	684F04EC92FDB71A0587910F5223F29B1B1126E69B049EA4E6C1AB3E32BCD103
Windows8.1-KB3161949-x64.msu	303F894A71FAD84F147E1EE715F8C60DDFC752D7	39F78CC8472AA4ACB6AF6BD18CC13BDEFB9728ED71FCEE2001E063683FED2B50
Windows8-RT-KB3161949-x64.msu	FD0D730F70653946886E358E9896364816937500	86967AF0963599C4E49835B35EF3A8A6BFA39FCBCB3C6DA378D02E70F34A023C
Windows6.0-KB3161949-x64.msu	E60F107F4F893C19885931B3C6121FDDF1150E52	D2F0E848E7D45C428324DD6833CE1F6B9E36F4EC0C27FA33993B482C20A870E0
Windows6.0-KB3161949-x86.msu	45C230D3302716D81E413BD233F953BD6F6F1F09	B45C8FB5F7E96CE551E752F67E45AAB6657B9E204C603F23AA7284BB39FA3E8D
Windows6.1-KB3161949-x86.msu	0055D0D1E103D374E042F31EBDD26931853B882B	F968AB471633DB7EBAF2619902CBB6246D14B14AF6E29CCA6C2981EB898DE0B7
Windows6.1-KB3161949-ia64.msu	9136B0FC403D6CDCD8CF94B061953CC11723CADB	7A2FFB83D4CE22325768FF94C71A9FFE839C653D1B8EA2C3BA73DDF89B2555C8
Windows6.1-KB3161949-x64.msu	E2372FB5746E9474CEC6EF1710F8D58EC5C6C000	7CFC5DCDDD7A72E1CB143E41A98D5EAF23CE554104F05311EFD8B317BCE8E847
Windows6.0-KB3161949-ia64.msu	2F913DA164CBAD6FD4331A9D06BA3F457EC6887F	540668B9660A8CD03240B7DCF84A9DFAEBCCBE3C4661340389FB0A049F317825

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File information

The English (United States) version of this software update installs files that have the attributes that are listed in the following tables. The dates and times for these files are listed in Coordinated Universal Time (UTC). Be aware that dates and times for these files on your local computer are displayed in your local time and with your current daylight saving time bias. The dates and times may also change when you perform certain operations on the files.Windows 8.1 and Windows Server 2012 R2 file informationNotes

• The files that apply to a specific product, milestone (RTM, SPn), and service branch (LDR, GDR) can be identified by examining the file version numbers as shown in the following table:
  Version| Product| Milestone| Service branch
  —|—|—|—
  6.3.960 0.16 xxx| Windows RT 8.1, Windows 8.1, and Windows Server 2012 R2| RTM| GDR
  6.3.960 0.17 xxx| Windows RT 8.1, Windows 8.1, and Windows Server 2012 R2| RTM| GDR
  6.3.960 0.18 xxx| Windows RT 8.1, Windows 8.1, and Windows Server 2012 R2| RTM| GDR

• GDR service branches contain only those fixes that are widely released to address widespread, critical issues. LDR service branches contain hotfixes in addition to widely released fixes.

• The MANIFEST files (.manifest) and MUM files (.mum) that are installed are not listed.
  For all supported x86-based versionsFile name| File version| File size| Date| Time| Platform| SP requirement| Service branch
  —|—|—|—|—|—|—|—
  Netbt.sys| 6.3.9600.18340| 213,504| 13-May-2016| 22:22| x86| None| Not applicable
  Mswsock.dll| 6.3.9600.18340| 286,208| 13-May-2016| 21:35| x86| SP_| X86_MICROSOFT-WINDOWS-W…-INFRASTRUCTURE-BSP
  Ws2_32.dll| 6.3.9600.18340| 320,720| 14-May-2016| 20:01| x86| None| Not applicable
  Winhttp.dll| 6.3.9600.18340| 631,808| 13-May-2016| 21:26| x86| None| Not applicable
  For all supported x64-based versionsFile name| File version| File size| Date| Time| Platform| SP requirement| Service branch
  —|—|—|—|—|—|—|—
  Netbt.sys| 6.3.9600.18340| 281,088| 13-May-2016| 23:07| x64| None| Not applicable
  Mswsock.dll| 6.3.9600.18340| 339,456| 13-May-2016| 21:58| x64| SP_| AMD64_MICROSOFT-WINDOWS-W…-INFRASTRUCTURE-BSP
  Ws2_32.dll| 6.3.9600.18340| 363,104| 14-May-2016| 20:01| x64| None| Not applicable
  Winhttp.dll| 6.3.9600.18340| 802,816| 13-May-2016| 21:45| x64| None| Not applicable
  Winhttp.dll| 6.3.9600.18340| 631,808| 13-May-2016| 21:26| x86| None| Not applicable
  Mswsock.dll| 6.3.9600.18340| 286,208| 13-May-2016| 21:35| x86| SP_| X86_MICROSOFT-WINDOWS-W…-INFRASTRUCTURE-BSP
  Ws2_32.dll| 6.3.9600.18340| 320,720| 14-May-2016| 20:01| x86| None| Not applicable
  Windows Server 2012 file informationNotes

• The files that apply to a specific product, milestone (RTM, SPn), and service branch (LDR, GDR) can be identified by examining the file version numbers as shown in the following table:
  Version| Product| Milestone| Service branch
  —|—|—|—
  6.2.920 0.17xxx| Windows 8, Windows RT, or Windows Server 2012| RTM| GDR
  6.2.920 0.21xxx| Windows 8, Windows RT, or Windows Server 2012| RTM| LDR

• GDR service branches contain only those fixes that are widely released to address widespread, critical issues. LDR service branches contain hotfixes in addition to widely released fixes.

• The MANIFEST files (.manifest) and MUM files (.mum) that are installed are not listed.
  For all supported x64-based versionsFile name| File version| File size| Date| Time| Platform| SP requirement| Service branch
  —|—|—|—|—|—|—|—
  Netbt.sys| 6.2.9200.21859| 318,976| 09-May-2016| 13:19| x64| None| Not applicable
  Mswsock.dll| 6.2.9200.21858| 355,328| 09-May-2016| 15:41| x64| SP_| AMD64_MICROSOFT-WINDOWS-W…-INFRASTRUCTURE-BSP
  Ws2_32.dll| 6.2.9200.21858| 343,552| 09-May-2016| 15:41| x64| None| Not applicable
  Winhttp.dll| 6.2.9200.21858| 711,680| 09-May-2016| 15:41| x64| None| Not applicable
  Winhttp.dll| 6.2.9200.21797| 516,096| 08-Mar-2016| 16:04| x86| None| Not applicable
  Mswsock.dll| 6.2.9200.21858| 288,768| 09-May-2016| 16:38| x86| SP_| X86_MICROSOFT-WINDOWS-W…-INFRASTRUCTURE-BSP
  Ws2_32.dll| 6.2.9200.21858| 307,712| 09-May-2016| 16:39| x86| None| Not applicable
  Windows Vista and Windows Server 2008 file informationNotes

• The files that apply to a specific product, milestone (RTM, SPn), and service branch (LDR, GDR) can be identified by examining the file version numbers as shown in the following table:
  Version| Product| Milestone| Service branch
  —|—|—|—
  6.0.600 2.19xxx| Windows Vista or Windows Server 2008| SP2| GDR
  6.0.600 2.23xxx| Windows Vista or Windows Server 2008| SP2| LDR

• GDR service branches contain only those fixes that are widely released to address widespread, critical issues. LDR service branches contain hotfixes in addition to widely released fixes.

• The MANIFEST files (.manifest) and MUM files (.mum) that are installed are not listed.
  For all supported x64-based versionsFile name| File version| File size| Date| Time| Platform| SP requirement| Service branch
  —|—|—|—|—|—|—|—
  Netbt.sys| 6.0.6002.19655| 248,320| 10-May-2016| 14:55| x64| None| Not applicable
  Netbtugc.exe| 6.0.6002.19655| 24,064| 10-May-2016| 14:55| x64| None| Not applicable
  Netbt.sys| 6.0.6002.23970| 248,320| 10-May-2016| 14:53| x64| None| Not applicable
  Netbtugc.exe| 6.0.6002.23970| 24,064| 10-May-2016| 14:53| x64| None| Not applicable
  Mswsock.dll| 6.0.6002.19655| 304,128| 10-May-2016| 15:54| x64| SP_| AMD64_MICROSOFT-WINDOWS-W…-INFRASTRUCTURE-BSP
  Mswsock.dll| 6.0.6002.23970| 303,616| 10-May-2016| 15:34| x64| SP_| AMD64_MICROSOFT-WINDOWS-W…-INFRASTRUCTURE-BSP
  Ws2_32.dll| 6.0.6002.19655| 264,704| 10-May-2016| 15:55| x64| None| Not applicable
  Ws2_32.dll| 6.0.6002.23970| 264,704| 10-May-2016| 15:35| x64| None| Not applicable
  Winhttp.dll| 6.0.6002.19655| 442,880| 10-May-2016| 15:54| x64| None| Not applicable
  Winhttp.dll| 6.0.6002.23970| 442,880| 10-May-2016| 15:35| x64| None| Not applicable
  Netbtugc.exe| 6.0.6002.19655| 21,504| 10-May-2016| 14:28| x86| None| Not applicable
  Netbtugc.exe| 6.0.6002.23970| 21,504| 10-May-2016| 14:28| x86| None| Not applicable
  Winhttp.dll| 6.0.6002.19655| 377,344| 10-May-2016| 15:31| x86| None| Not applicable
  Winhttp.dll| 6.0.6002.23970| 377,344| 10-May-2016| 15:14| x86| None| Not applicable
  Mswsock.dll| 6.0.6002.19655| 223,232| 10-May-2016| 15:31| x86| SP_| X86_MICROSOFT-WINDOWS-W…-INFRASTRUCTURE-BSP
  Mswsock.dll| 6.0.6002.23970| 223,232| 10-May-2016| 15:14| x86| SP_| X86_MICROSOFT-WINDOWS-W…-INFRASTRUCTURE-BSP
  Ws2_32.dll| 6.0.6002.19655| 179,200| 10-May-2016| 15:31| x86| None| Not applicable
  Ws2_32.dll| 6.0.6002.23970| 179,200| 10-May-2016| 15:14| x86| None| Not applicable
  For all supported x86-based versionsFile name| File version| File size| Date| Time| Platform| SP requirement| Service branch
  —|—|—|—|—|—|—|—
  Netbt.sys| 6.0.6002.19655| 185,856| 10-May-2016| 14:28| x86| None| Not applicable
  Netbtugc.exe| 6.0.6002.19655| 21,504| 10-May-2016| 14:28| x86| None| Not applicable
  Netbt.sys| 6.0.6002.23970| 186,368| 10-May-2016| 14:28| x86| None| Not applicable
  Netbtugc.exe| 6.0.6002.23970| 21,504| 10-May-2016| 14:28| x86| None| Not applicable
  Mswsock.dll| 6.0.6002.19655| 223,232| 10-May-2016| 15:31| x86| SP_| X86_MICROSOFT-WINDOWS-W…-INFRASTRUCTURE-BSP
  Mswsock.dll| 6.0.6002.23970| 223,232| 10-May-2016| 15:14| x86| SP_| X86_MICROSOFT-WINDOWS-W…-INFRASTRUCTURE-BSP
  Ws2_32.dll| 6.0.6002.19655| 179,200| 10-May-2016| 15:31| x86| None| Not applicable
  Ws2_32.dll| 6.0.6002.23970| 179,200| 10-May-2016| 15:14| x86| None| Not applicable
  Winhttp.dll| 6.0.6002.19655| 377,344| 10-May-2016| 15:31| x86| None| Not applicable
  Winhttp.dll| 6.0.6002.23970| 377,344| 10-May-2016| 15:14| x86| None| Not applicable
  For all supported ia64-based versionsFile name| File version| File size| Date| Time| Platform| SP requirement| Service branch
  —|—|—|—|—|—|—|—
  Netbt.sys| 6.0.6002.19655| 632,832| 10-May-2016| 14:37| IA-64| None| Not applicable
  Netbtugc.exe| 6.0.6002.19655| 52,224| 10-May-2016| 14:36| IA-64| None| Not applicable
  Netbt.sys| 6.0.6002.23970| 632,832| 10-May-2016| 14:38| IA-64| None| Not applicable
  Netbtugc.exe| 6.0.6002.23970| 52,224| 10-May-2016| 14:37| IA-64| None| Not applicable
  Mswsock.dll| 6.0.6002.19655| 709,632| 10-May-2016| 15:23| IA-64| SP_| IA64_MICROSOFT-WINDOWS-W…-INFRASTRUCTURE-BSP
  Mswsock.dll| 6.0.6002.23970| 709,120| 10-May-2016| 15:12| IA-64| SP_| IA64_MICROSOFT-WINDOWS-W…-INFRASTRUCTURE-BSP
  Ws2_32.dll| 6.0.6002.19655| 519,168| 10-May-2016| 15:23| IA-64| None| Not applicable
  Ws2_32.dll| 6.0.6002.23970| 519,168| 10-May-2016| 15:13| IA-64| None| Not applicable
  Winhttp.dll| 6.0.6002.19655| 962,048| 10-May-2016| 15:23| IA-64| None| Not applicable
  Winhttp.dll| 6.0.6002.23970| 962,048| 10-May-2016| 15:13| IA-64| None| Not applicable
  Netbtugc.exe| 6.0.6002.19655| 21,504| 10-May-2016| 14:28| x86| None| Not applicable
  Netbtugc.exe| 6.0.6002.23970| 21,504| 10-May-2016| 14:28| x86| None| Not applicable
  Winhttp.dll| 6.0.6002.19655| 377,344| 10-May-2016| 15:31| x86| None| Not applicable
  Winhttp.dll| 6.0.6002.23970| 377,344| 10-May-2016| 15:14| x86| None| Not applicable
  Mswsock.dll| 6.0.6002.19655| 223,232| 10-May-2016| 15:31| x86| SP_| X86_MICROSOFT-WINDOWS-W…-INFRASTRUCTURE-BSP
  Mswsock.dll| 6.0.6002.23970| 223,232| 10-May-2016| 15:14| x86| SP_| X86_MICROSOFT-WINDOWS-W…-INFRASTRUCTURE-BSP
  Ws2_32.dll| 6.0.6002.19655| 179,200| 10-May-2016| 15:31| x86| None| Not applicable
  Ws2_32.dll| 6.0.6002.23970| 179,200| 10-May-2016| 15:14| x86| None| Not applicable
  Windows 7 and Windows Server 2008 R2 file informationNotes

• The files that apply to a specific product, milestone (RTM, SPn), and service branch (LDR, GDR) can be identified by examining the file version numbers as shown in the following table:
  Version| Product| Milestone| Service branch
  —|—|—|—
  6.1.760 1.18xxx| Windows 7 or Windows Server 2008 R2| SP1| GDR
  6.1.760 1.23 xxx| Windows 7 or Windows Server 2008 R2| SP1| LDR

• GDR service branches contain only those fixes that are widely released to address widespread, critical issues. LDR service branches contain hotfixes in addition to widely released fixes.

• The MANIFEST files (.manifest) and MUM files (.mum) that are installed are not listed.
  For all supported x86-based versionsFile name| File version| File size| Date| Time| Platform| SP requirement| Service branch
  —|—|—|—|—|—|—|—
  Netbt.sys| 6.1.7601.23451| 188,928| 11-May-2016| 14:52| x86| None| Not applicable
  Netbtugc.exe| 6.1.7601.23451| 26,624| 11-May-2016| 15:01| x86| None| Not applicable
  Mswsock.dll| 6.1.7601.23451| 231,424| 11-May-2016| 15:19| x86| SP_| X86_MICROSOFT-WINDOWS-W…-INFRASTRUCTURE-BSP
  Ws2_32.dll| 6.1.7601.23451| 206,336| 11-May-2016| 15:19| x86| None| Not applicable
  Winhttp.dll| 6.1.7601.23451| 351,744| 11-May-2016| 15:19| x86| None| Not applicable
  For all supported ia64-based versionsFile name| File version| File size| Date| Time| Platform| SP requirement| Service branch
  —|—|—|—|—|—|—|—
  Netbt.sys| 6.1.7601.23451| 616,960| 11-May-2016| 14:44| IA-64| None| Not applicable
  Netbtugc.exe| 6.1.7601.23451| 53,760| 11-May-2016| 14:58| IA-64| None| Not applicable
  Mswsock.dll| 6.1.7601.23451| 750,592| 11-May-2016| 15:13| IA-64| SP_| IA64_MICROSOFT-WINDOWS-W…-INFRASTRUCTURE-BSP
  Ws2_32.dll| 6.1.7601.23451| 546,304| 11-May-2016| 15:13| IA-64| None| Not applicable
  Winhttp.dll| 6.1.7601.23451| 812,032| 11-May-2016| 15:13| IA-64| None| Not applicable
  Netbtugc.exe| 6.1.7601.23451| 26,624| 11-May-2016| 15:01| x86| None| Not applicable
  Winhttp.dll| 6.1.7601.23451| 351,744| 11-May-2016| 15:19| x86| None| Not applicable
  Mswsock.dll| 6.1.7601.23451| 231,424| 11-May-2016| 15:19| x86| SP_| X86_MICROSOFT-WINDOWS-W…-INFRASTRUCTURE-BSP
  Ws2_32.dll| 6.1.7601.23451| 206,336| 11-May-2016| 15:19| x86| None| Not applicable
  For all supported x64-based versionsFile name| File version| File size| Date| Time| Platform| SP requirement| Service branch
  —|—|—|—|—|—|—|—
  Netbt.sys| 6.1.7601.23451| 262,144| 11-May-2016| 14:58| x64| None| Not applicable
  Netbtugc.exe| 6.1.7601.23451| 25,088| 11-May-2016| 15:11| x64| None| Not applicable
  Mswsock.dll| 6.1.7601.23451| 327,168| 11-May-2016| 17:02| x64| SP_| AMD64_MICROSOFT-WINDOWS-W…-INFRASTRUCTURE-BSP
  Ws2_32.dll| 6.1.7601.23451| 296,448| 11-May-2016| 17:02| x64| None| Not applicable
  Winhttp.dll| 6.1.7601.23451| 444,928| 11-May-2016| 17:02| x64| None| Not applicable
  Netbtugc.exe| 6.1.7601.23451| 26,624| 11-May-2016| 15:01| x86| None| Not applicable
  Winhttp.dll| 6.1.7601.23451| 351,744| 11-May-2016| 15:19| x86| None| Not applicable
  Mswsock.dll| 6.1.7601.23451| 231,424| 11-May-2016| 15:19| x86| SP_| X86_MICROSOFT-WINDOWS-W…-INFRASTRUCTURE-BSP
  Ws2_32.dll| 6.1.7601.23451| 206,336| 11-May-2016| 15:19| x86| None| Not applicable