"Device does not exist" error after you reinsert a USB COM port device

Applies to: Windows Server 2012 R2 DatacenterWindows Server 2012 R2 StandardWindows Server 2012 R2 Essentials


USB devices that expose COM ports for communicating between their application and the device use the inbox Usbser.sys to create virtual COM ports in Windows 8.1, Windows Server 2012 R2, Windows 7, or Windows Server 2008 R2. If such a device is removed and then reinserted quickly, it may not be rediscovered correctly, and the COM port, such as COM3, may not be re-created. Additionally, you may receive an error message that resembles the following:

Device does not exist.


This problem occurs because of a race condition in the Usbser.sys driver during surprise removal and rediscovery of the same device. This causes the corresponding COM port not to be re-created.


To resolve this issue, we have released a hotfix for Windows 7 and Windows Server 2008 R2, and we have released an update rollup for Windows 8.1 and Windows Server 2012 R2.

Get the update rollup for Windows 8.1 and Windows Server 2012 R2

To resolve this issue, install the December 2014 update rollup for Windows RT 8.1, Windows 8.1, and Windows Server 2012 R2.

Get the hotfix for Windows 7 and Windows Server 2008 R2

A supported hotfix is available from Microsoft Support. However, this hotfix is intended to correct only the problem that is described in this article. Apply this hotfix only to systems that are experiencing the problem described in this article. This hotfix might receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next software update that contains this hotfix.

If the hotfix is available for download, there is a "Hotfix download available" section at the top of this Knowledge Base article. If this section does not appear, contact Microsoft Customer Service and Support to obtain the hotfix.

Note If additional issues occur or if any troubleshooting is required, you might have to create a separate service request. The usual support costs will apply to additional support questions and issues that do not qualify for this specific hotfix. For a complete list of Microsoft Customer Service and Support telephone numbers or to create a separate service request, go to the following Microsoft website: Note The "Hotfix download available" form displays the languages for which the hotfix is available. If you do not see your language, it is because a hotfix is not available for that language.


To apply this hotfix, you must have Service Pack 1 for Windows 7 or Windows Server 2008 R2 installed. Additionally, you must have security update 2884256 installed.

Restart requirement

You must restart the computer after you apply this hotfix.

Hotfix replacement information

This hotfix does not replace any previously released hotfix.


Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.


Learn about the terminology that Microsoft uses to describe software updates.