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Windows 10 Patch- KB4056892

UPDATE February 2018 - No Further Action Required

Windows 10 v1709 KB4058258 released January 31, 2018 corrects, among other fixes, the errors introduced in KB4056892 described below.

The Windows 10 patch (KB 4056892 for build 1709) released in January 2018 caused issues with a lot of ASCOM drivers, clients, and other COM Servers due to a known issue in the patch (1). This has been posted in detail on the ASCOM user group (2). You can see an example of the issue from Bob Denny’s forum at dc3 (3). Basically if you try to use an affected ASCOM driver or client you will get a very nasty security warning followed by a load failure or a crash.

I have been running some tests and most of Optec’s drivers seem to be fine and require no changes. However several client programs that use our drivers seem to be having issues. For example on a test system I cannot load the FocusLynx driver in POTH but when I apply the fix to POTH I can load the FocusLynx driver without changing the driver settings.

Bob Denny, of DC-3 Dreams and ACP, has a very nice write up explaining how to fix drivers and clients available here:


You should only use this fix if you are running Windows 10 and are having this problem. I would record what you change and only fix the things that you find are having problems.

So far in our testing the only Optec drivers that seem to need this change are also ASCOM clients. These are the Optec ASCOM Server, Optec Perseus Driver, and Optec Alt-Az Server. In addition you may need to fix other drivers if those drivers are required for these products or for FocusLock. You will find the names for our drivers as seen in the Component Services below. For FocusLock you will likely need to fix TheSkyX’s and MaxIm’s API connections if they are used.  

ASCOM Initiative FixDCOM package

UPDATE 17-Jan-2018: The ASCOM Initiative has provided a tool for making the security change to EXE drivers, elimininating the need to do the procedure below for EXE ASCOM drivers. You may still need to make this change to programs that have Programming Interfaces used by other programs, so we're leaving the manual instructions below. The tool is located at:



Driver name as seen in Component Services:

Optec Alt-Az Server: This project creates a Telescope and Rotator Driver for Alt-Az derotation usage.

Optec ASCOM Server: ASCOM multi-interface server for OptecASCOMServer

Perseus Driver: ASCOM multi-interface server for Perseus Server


Non-Optec names but useful to know:

MaxIm in 32-bit DCOMCNFG: MaxIm.CCDCamera

Poth: ASCOM Focuser driver for POTH

TheSkyX: TheSkyX and TheSkyXAdaptor


Other useful sources of information:

(1)    https://support.microsoft.com/en-us/help/4056892/windows-10-update-kb4056892

(2)    https://groups.yahoo.com/neo/groups/ASCOM-Talk/conversations/topics/38536

(3)    https://forums.dc3.com/showthread.php?11182-ALERT-Windows-10-Update-KB4056892-Reported-Problems&p=67732#post67732