Microsoft Office Memory Corruption Vulnerability

2016-07-12T07:00:00
ID MS:CVE-2016-3280
Type mscve
Reporter Microsoft
Modified 2016-07-12T07:00:00

Description

A remote code execution vulnerability exists in Microsoft Office software when the Office software fails to properly handle objects in memory. An attacker who successfully exploited the vulnerability could run arbitrary code in the context of the current user. If the current user is logged on with administrative user rights, an attacker could take control of the affected system. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights. Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights.

Exploitation of the vulnerability requires that a user open a specially crafted file with an affected version of Microsoft Office software. In an email attack scenario, an attacker could exploit the vulnerability by sending the specially crafted file to the user and convincing the user to open the file. In a web-based attack scenario, an attacker could host a website (or leverage a compromised website that accepts or hosts user-provided content) that contains a specially crafted file designed to exploit the vulnerability. An attacker would have no way to force users to visit the website. Instead, an attacker would have to convince users to click a link, typically by way of an enticement in an email or instant message, and then convince them to open the specially crafted file.

Note that where severity is indicated as Critical in the Affected Products table, the Preview Pane is an attack vector.

The security update addresses the vulnerability by correcting how Office handles objects in memory.

Use Microsoft Office File Block policy to prevent Office from opening RTF documents from unknown or untrusted sources. Warning If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.

For Office 2007

  1. Run regedit.exe as Administrator and navigate to the following subkey: [HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\12.0\Word\Security\FileOpenBlock]
  2. Set the RtfFiles DWORD value to 1. Note To use 'FileOpenBlock' with Office 2007, all of the latest Office 2007 security updates as of May 2007 must be applied.

For Office 2010

  1. Run regedit.exe as Administrator and navigate to the following subkey: [HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Word\Security\FileBlock]
  2. Set the RtfFiles DWORD value to 2.
  3. Set the OpenInProtectedView DWORD value to 0.

For Office 2013

  1. Run regedit.exe as Administrator and navigate to the following subkey: [HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\Word\Security\FileBlock]
  2. Set the RtfFiles DWORD value to 2.
  3. Set the OpenInProtectedView DWORD value to 0.

Impact of Workaround. Users who have configured the File Block policy and have not configured a special “exempt directory” as discussed in Microsoft Knowledge Base Article 922849 will be unable to open documents saved in the RTF format.

How to undo the workaround For Office 2007

  1. Run regedit.exe as Administrator and navigate to the following subkey: [HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\12.0\Word\Security\FileOpenBlock]
  2. Set the RtfFiles DWORD value to 0.

For Office 2010

  1. Run regedit.exe as Administrator and navigate to the following subkey: [HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Word\Security\FileBlock]
  2. Set the RtfFiles DWORD value to 0.
  3. Leave the OpenInProtectedView DWORD value set to 0.

For Office 2013

  1. Run regedit.exe as Administrator and navigate to the following subkey: [HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\Word\Security\FileBlock]
  2. Set the RtfFiles DWORD value to 0.
  3. Leave the OpenInProtectedView DWORD value set to 0.

Prevent Word from loading RTF files Warning If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.

Interactive managed script method For Word 2007

  1. Click Start, click Run, in the Open box, type regedit, and then click OK.
  2. Locate and then click the following registry subkey: HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\12.0\Word\Security\FileOpenBlock Note that if the FileOpenBlock subkey does not exist, you must create it. To do this, follow these steps:
    1. Select the Security subkey.
    2. On the Edit menu, point to New, and then click Key.
    3. Type FileOpenBlock, and then press Enter.
  3. After you select the FileOpenBlock subkey, locate the DWORD value RtfFiles. Note that if this value does not exist, you must create it. To do this, follow these steps:
    1. On the Edit menu, point to New, and then click DWORD value.
    2. Type RtfFiles and then press Enter.
    3. Right-click RtfFiles and then click Modify.
    4. In the Value data box, type 1, and then click OK.
    5. On the File menu, click Exit to exit Registry Editor.

Managed deployment script method For Word 2007

  1. Save the following to a file with a .reg extension (For example Disable_RTF_In_Word.reg):

    [HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\12.0\Word\Security\FileOpenBlock]
    "RtfFiles"=dword:00000001
    
  2. Run the above registry script created in step 1 on the target machine with the following command from an administrator command prompt: Regedit / s Disable_RTF_In_Word.reg Note RTF files will not be readable by Word.