MS16-077: 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.
  • This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:
    322756 How to back up and restore the registry in Windows

Note You must restart the computer after you make any of the registry changes described in the following section in order for the changes to take effect.

Behavior changes after installation

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

  • The computer does not respond to NetBIOS name resolution requests from IP addresses that are not on the same subnet.
  • The computer does not respond to nbtstat -a or nbtstat -A requests from IP addresses that are not on the same subnet.
  • 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 both of the following registry entries: 

    SUBKEY: HKEY_LOCAL_MACHINE\SOFTWARE\WoW6432Node\Microsoft\Windows\CurrentVersion\Internet Settings\WinHttp
    Value Name: AutoProxyAutoLogonIfChallenged
    Type: DWORD
    Value: 1
    Default value of the flag: 0

    SUBKEY: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\WinHttp
    Value Name: AutoProxyAutoLogonIfChallenged
    Type: DWORD
    Value: 1
    Default value of the flag: 0




Additional information about this security update

The following articles contain additional information about this security update as it relates to individual product versions. The articles may contain known issue information.
  • 3161949 MS16-077: Description of the security update for WPAD: June 14, 2016
  • 3163017 Cumulative update for Windows 10: June 14, 2016
  • 3163018 Cumulative update for Windows 10 Version 1511 and Windows Server 2016 Technical Preview 4: June 14, 2016

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

More Information

Security update deployment information
How to obtain help and support for this security update
Властивості

Ідентифікатор статті: 3165191 – останній перегляд: 22 вер. 2016 р. – виправлення: 1

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