Microsoft plans a Windows 10 V1803 SMBv1 fix on June 2018

[German]Just a brief information for users of the Windows 10 April Update who runs into network issues with and possibly with multi-function devices (scanners using a scan to network shares). It seems that Microsoft is working on a fix for the 'SMBv1 isses' and plans to release a patch in June (patchday would be June 12, 2018). Microsoft has fixed this issue – see my addendum.


Some background about the network SMBv1 issue

Microsoft had already announced since summer 2017 that support for the SMBv1 protocol in Windows 10 will expire. The abbreviation SMB stands for Server Message Block (former names are LAN Manager or NetBIOS protocol), a network protocol for file, print and other server services in computer networks. Version 1 (SMBv1) of the network protocol designed over 30 years ago, and especially the Microsoft implementation, is considered very error-prone and security-critical (see Microsoft plans to deactivate SMBv1 in  Windows 10 V1709 and StopUsingSMB1).

In the meantime there are SMBv2 and SMBv3, so that the use of SMBv1 in Windows networks is no longer absolutely necessary. For example, Windows Vista is no longer dependent on SMBv1 because SMBv2 is used there.

What's the problem?

For new installations of Windows 10 it was at least since Windows 10 V1709 that SMBv1 was deactivated. If devices required SMBv1, the administrator had to activate SMBv1 again via Windows features (see also).

Windows Features SMB 1.0/CIFS

With Windows 10 V1803, however, the 'missing SMBv1' problem has probably hit a lot of people, because this build also brings a change after upgrade. If the SMBv1 client is not used for a total of 15 days (except when the computer is turned off), Windows 10 April Update automatically uninstalls the SMBv1 client (see this Microsoft article and my blog post Windows 10: Scanner fails after update). But re-enabling SMBv1 in Windows 10 V1803 doesn't fix all network issues.


Some changes in KB4103721, KB4100403

In May 2018 Microsoft released the updates KB4103721 (05/08/2018) and KB4100403 (05/23/2018) for Windows 10 V1803. However, after upgrading to Windows 10 V1803 or installing these updates, users of Windows 10 April Update seem to experience issues when using the SMBv1 protocol. I noticed postings in the Microsoft-Answers forums, where my hint to try to activate SMBv1 once did not bring a success. I couldn't figure it out at first. Now Microsoft has added the following paragraph in the 'Known issues' section to the two KB articles mentioned above.

Some users running Windows 10 version 1803 may receive an error "An invalid argument was supplied" when accessing files or running programs from a shared folder using the SMBv1 protocol.

The site The Register noticed that, and Microsoft wrote about the know issue within the kb articles:

Enable SMBv2 or SMBv3 on both the SMB server and the SMB client, as described in KB2696547. Microsoft is working on a resolution that will be available later in June.

It is correct to switch to SMBv2 or SMBv3 in your environment (clients and servers) to solve the security problem associated with SMBv1. But there are also scenarios where SMBv1 is mandatory (if a client or server, like a NAS drive, an All-in-One printer etc., which supports only SMBv1 from the firmware). Then you need to activate SMBv1 for a transition time.

Some background about the SMBv1 bug

So Microsoft says, that there is an issue in SMBv1 for Windows 10 V1803. Let's see, whether we can get more details. The Register has a possible hint, pointing to a MSDN forum discussion. Within the thread RS4:1803]Windows 10 1803 won't run ODBC SQL connected application from network, there are more details. The thread creator wrote:

  • We have an application that runs from a network location. It has always worked fine in Windows 10 through latest cumulative 1709 builds. Since updating online to 1803 (17134.1) it will not run from the network.
  • With an ODBC SQL connection, from Windows 10 Build 17134.1 (the RTM of the Windows 10 April Update) an access error occurs (e.g. to Oracle databases in the network).
  • SMB 1.0/CIFS is enabled for client and server shares, so it should work with shared network accesses.

The thread starter was able to solve his issue activating SMBv2. But if you depend on SMBv1 (see my notes above), you won't get any further. Within the thread, user Nicolas Casas then posted a possible explanation:

you are pointing something. I have the same issue , that is running an exe from a SMB1 network share
Since windows 10 1803 update the sql server access was filtered that way
but on one PC it was working. this one runs Avast as well.
so I did a fresh installation of 1803, manually enabled SMB1 in windows with

dism /online /enable-feature /featurename:SMB1Protocol-Server

and SQL access was not working. I then installed avast latest free version
and it worked! Additionnaly I uninstalled Avast.. and blocked again. so … I look on Defender firewall to add the application in the list, disabled defender but no way to succeed yet

Within the MSDN forum thread other users confirmed similar observations with other third-party virus scanners. It appears that Windows Defender in combination with Windows Firewall causes an issue with SMBv1 shares.

Some workarounds

If you depend to access network shares with SMBv1, you can install Avast Free or a third-party firewall so that Windows Defender and Windows Firewall are turned off, and it works. Just crazy.

For a Windows 10 V1803 network environment, Microsoft has outlined a possible workaround without activating the SMBv1 protocol within this article (section Explorer Network Browsing).

For All-in-One printers with a failing scan to network share function, read my blog post Windows 10: Scanner fails after update. Overall we need to wait and see, if and what Microsoft will present us on June 2018 patchday (06/12/2018).

Addendum: Final Fix with Update KB4284848

Microsoft released Update KB4284848 for Windows 10 V1803, which also contains a fix for the SMBv1 issue (see also PSA: Windows 10 V1803: Update KB4284848 brings SMBv1 fix).

Similar articles:
Microsoft plans to deactivate SMBv1 in  Windows 10 V1709
Windows 10: Scanner fails after update
Windows 10: Issues with WSUS and Store (V1803)
Windows 10: 'An App default was reset'
Windows 10 V1803: Update KB4100403 (with SSD fix)
Windows 10 V1803: Fix for Explorer Timeline crashes
Windows 10 V1803: (Boot-) issues with update KB4103721
Windows 10 V1803 Feature Upgrade and AVAST damages
Windows 10 V1803: Rollout stopped for Intel SSDs
Windows 10 Fall April Update – Upgrade Tips
Media Feature Pack for Windows 10 N Version 1803
Windows 10 security updates May 8, 2018

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5 Responses to Microsoft plans a Windows 10 V1803 SMBv1 fix on June 2018

  1. Matt klueppel says:

    User "A" on one of the Windows 10 machines I manage can no longer access our internal MS SQL Server database from applications executed from a shared network drive.

    The machine is Windows 10 build 1803

    User "B" profile on the same machine does not exhibit this problem

  2. Murray360 says:

    Windows defender is not the problem . Even eradicating it from win10 the problem remains . What avast and AVG do is install a filter driver that changes in some way some parameters during socket creation call . This way you are granted access to net functionality even if the program is launched from SMBv1 share.

  3. Dexter says:

    I'm experiencing this exact same problem. As soon as a machine gets the KB4100403 update, it can no longer access our SQL server.

    This "update" is on the verge of shutting down our hotel! Only 1 machine is still able to access the property management system!

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  5. Murray360 says:


    You could try the fix i proposed on Microsoft forum thread about ODBC not working .

    For me it worked , at least as temporary fix .

    Good luck

  6. Steve Johnson says:

    Good Morning,

    I'm seeing this issue a lot. I'm a field service technician in the copier industry, and there are a couple of things you might want to look into to keep this from happening.

    Some copiers are unable to scan to SMB v2/v3, because they lack the right firmware to handle the increased security. This is also true of machines set up with "Scan to Email". Updates to SSL and TLS encryption require an update to your Multifunction Device as well. Contact your copier service provider and they can send a technician to install that firmware for you.

    Copiers older than 7 years may or may NOT be able to be updated. Some manufacturers won't write a firmware file for equipment that they consider obsolete. Once again….check with your copier service provider.

    I hope this helps.


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