Office File Validation causes slow opening of Excel files from network

Office File Validation, or OFV, was a new security feature (an add-in) released in Office 2010 and is installed as part of MS11-021, released in April 2011. It was back ported to Office 2007 and 2003. KB Article 2501584 states, “Office File Validation verifies that a particular binary file complies with the application’s expectations. Office File Validation can help prevent unknown binary file format attacks against Microsoft Office 97-2003 file formats. ” (

However we have seen situations where, after applying MS11-021, opening Office files is significantly slower from a network location. KB Article 2570623 ( was written for this purpose. The problem typically only affects Excel 2003, however it can affect Excel 2007 and 2010 if you have ever set the ‘DisableRobustifiedUNC’ registry key. If you’re using Excel 2003 and are seeing an increase in time taken to open Excel files from a network location, like 40 seconds to 5 minutes, then you will want to check out KB article 2570623 ( If you are on Office 2007 or 2010 and see an increase in time to open Excel files across the network and you can confirm that MS11-021 was recently installed, then check for the following registry key:

For Excel 2007


For Excel 2010


Look for a DWORD value labeled DisableRobustifiedUNC set to a value of 1. If this is set on your machine, it’s recommended you delete this value or set the DWORD value to 0.


Comments (8)

  1. Anonymous says:

    Solve given trouble with microsoft excel file fix

  2. Anon says:

    Should this be listed as a known issue in 2489279?

  3. Galenklein says:

    he didn't post if this was the reg for xp, vist, or 7. i couldn't find the key for excel 2010. i think they need to come out with a sevice pack to fix this issue. i work in the business environment and this is becoming a hugh issue for me.

  4. zamage says:

    Excel Slow to open on network drive.


    Disable SMB 2.0.

    You need to apply the fix (below) to both the "client" and the "server" operating systems.


    To disable SMB 2.0 for Windows Vista, Windows 7 or Windows systems that are the “client” systems run the following two commands:

    sc config lanmanworkstation depend= bowser/mrxsmb10/nsi

    sc config mrxsmb20 start= disabled

    Note there's an extra " " (space) after the "=" sign.


    Run "regedit" on Windows Server 2008 based computer.

    Expand and locate the sub tree as follows.


    Add a new REG_DWORD key with the name of "Smb2" (without quotation mark)

    Value name: Smb2

    Value type: REG_DWORD

    0 = disabled

    Set the value to 0 to disable SMB 2.0.

    Reboot the server.

    Issue is fixed

  5. Chris Edwards says:

    In addition to this, it's possible for the tmp files to fill up so much as to cause several seconds delay opening files.  We have an automated file processor that reads several hundred excel files to combine data from them.  On a clean PC, opening 60 files via automation took 10 seconds.  On the machine that was used regularly for the task, it took 250 seconds.  The cause was >65000 xxxx.tmp files in the users<name>AppDataLocalTemp folder.  Excel tries to pick a random 4-hex char filename, but once most of them are taken, filename collisions are excessive.  In the extreme, the Open method fails completely. ( "unable to get the Open property of the Workbooks class" )

  6. Fevington says:

    Slight variation on the above was required for me on my W8 laptop. The DWORD value was not in the registry but after I created it and set the value to zero AND rebooted, the problem was resolved.

  7. Alfredo says:

    In our enviroment,we just migrated to Windows 7 64bit – Office 2010 w/ SP2 32bit. we were experiencing this exact issue, once we created this key (key not present in registry). All my slowness/not saving issues were solved!

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