MS16-070 - Critical: Security Update for Microsoft Office (3163610) - Version: 1.0

Multiple Microsoft Office Memory Corruption Vulnerabilities

Multiple remote code execution vulnerabilities exist in Microsoft Office software when the Office software fails to properly handle objects in memory. An attacker who successfully exploited the vulnerabilities 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 vulnerabilities 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 vulnerabilities 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 that is designed to exploit the vulnerabilities. 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 Messenger message, and then convince them to open the specially crafted file.

Note that where the severity is indicated as Critical in the Affected Software and Vulnerability Severity Ratings table, the Preview Pane is an attack vector for CVE-2016-0025. The security update addresses the vulnerability by correcting how Office handles objects in memory.

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
Microsoft Office Memory Corruption Vulnerability	CVE-2016-0025	No	No
Microsoft Office Memory Corruption Vulnerability	CVE-2016-3233	No	No

Mitigating Factors

Microsoft has not identified any mitigating factors for these vulnerabilities.

Workarounds

Microsoft has not identified any workarounds for this vulnerability.

Microsoft Office Information Disclosure Vulnerability – CVE-2016-3234

An information disclosure vulnerability exists when Microsoft Office improperly discloses the contents of its memory. An attacker who exploited the vulnerability could use the information to compromise the user’s computer or data. To exploit the vulnerability, an attacker could craft a special document file, and then convince the victim to open it. An attacker must know the memory address location where the object was created. The update addresses the vulnerability by changing the way certain functions handle objects in memory.

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
Microsoft Office Information Disclosure Vulnerability	CVE-2016-3234	No	No

Mitigating Factors

Microsoft has not identified any mitigating factors for this vulnerability.

Workarounds

The following workaround may be helpful in your situation:

Workaround for CVE-2016-3234

• 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.

Microsoft Office OLE DLL Side Loading Vulnerability – CVE-2016-3235

A remote code execution vulnerability exists when Windows improperly validates input before loading libraries. An attacker who successfully exploited the vulnerability could take control of an 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.

To exploit the vulnerability, an attacker would need access to the local system and the ability to execute a specially crafted application on the system. The security update addresses the vulnerability by correcting how Windows validates input before loading libraries.

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
Microsoft Office OLE DLL Side Loading Vulnerability	CVE-2016-3235	No	No

Mitigating Factors

Microsoft has not identified any mitigating factors for these vulnerabilities.

Workarounds

Microsoft has not identified any workarounds for this vulnerability.

from Microsoft Security Bulletins http://ift.tt/1Q1r8vJ