MS15-074: Vulnerability in Windows Installer service could allow elevation of privilege: July 14, 2015

Applies to: Windows Server 2012 R2 DatacenterWindows Server 2012 R2 StandardWindows Server 2012 R2 Essentials


This security update resolves a vulnerability in Windows that could allow elevation of privilege if the Windows Installer service incorrectly runs custom action scripts. To exploit the vulnerability, an attacker must first compromise a user who is logged on to the target system. An attacker could then install programs, could view, change, or delete data, or could create new accounts by having full administrative rights. To learn more about the vulnerability, see Microsoft Security Bulletin MS15-074.

More Information

  • All future security and nonsecurity 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 require before you install this update. For more information, see Add language packs to Windows.
Information for installations that are dependent on the less-secure behavior
ImportantFollow the steps in this section carefully. Serious problems might occur if you modify the registry incorrectly. Before you modify it, back up the registry for restoration in case problems occur.
  • Applications that use installations that are dependent on the less-secure behavior may not install correctly. If it is critical that installation for these applications be enabled, IT administrators can temporarily opt-out of this security fix by changing a registry setting.

    Note Be aware that this opt-out method disables this security fix.

    To temporarily undo the security fix in KB 3072630, follow these steps:
    1. Click Start, click Run, type regedit in the Open box, and then click OK.
    2. Locate and then click the following subkey in the registry:

      Note If this subkey does not exist, create it.
    3. On the Edit menu, point to New, and then click DWORD Value.
    4. For the DWORD name, type RemappedElevatedProxiesPolicy, and then press Enter.
    5. Right-click RemappedElevatedProxiesPolicy, and then click Modify.
    6. In the Value data box, type 1, and then click OK.
    7. Install the required application.
    8. After the application installs successfully, reset the RemappedElevatedProxiesPolicy DWORD value to 0 to re-enable the security fix for KB 3072630.
After you install this security update, the behavior of custom actions for accessing user hives in the registry will have changed. This security update more strictly enforces the requirement that only custom actions that use impersonation can access HKCU for the current user.

The following is the new behavior:
  • Custom actions with impersonation can access HKCU for the current user.
  • Custom action that run as System will access HKCU for System instead of HKCU for the current user.
After you install this security update, if you find that some registry keys in HKCU are no longer set by custom actions, you may have to re-design the MSI package so that this custom action is impersonated.

Known issues in this security update

  • 3153727 Windows Installer with certain actions can't be installed on Windows Server 2012 R2 or Windows Server 2008 R2 SP1

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

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.