Windows 7: Preview Rollup Update KB4088881 (03/23/2018)

Windows Update[German]Microsoft released Preview Rollup Update KB4088881 for Windows 7 Service Pack 1 and Windows Server 2008 R2 Service Pack 1 on March 23, 2018. Here is some information about the update and the answer whether you should install the update or not.


In March 2018 we have a kind of 'scattered' preview rollups. I would have expected the preview rollups on the 3rd Tuesday of each month, March 21, 2018. But the release of updates has been delayed. For Windows 8.1 the rollup update came on March 22, 2018 (see Updates for Windows 8.1/Windows Server 2012/R2 (03/21/2018)) and the link list at the end of the article).

Updates for Windows 7 SP1 and Windows Server 2008 R2 are documented by Microsoft (occasionally delayed by a few hours to days) on this website.

What are Preview Rollup Updates?

Since not all blog readers are familiar with the nomenclature, today a little refresher on these topic. Microsoft has been using rollup updates for Windows 7 and Windows 8.1 and its server counterparts since October 2016. These contain the updates of the previous month as well as the latest patches. The rollup updates are released for Windows on Tuesday 2nd of each month.

The preview rollup update is scheduled for Tuesday 3rd of each month. This is the preview of the rollup updates for the following month. In the current case, the preview rollup update of March 2018 gives us a preview of the April 2018 rollup update; if you want to read the details, I explained this in more Details within my German blog posts below (unfortunately only available in German).

Patchday-Infos: Was ab Oktober für Windows 7/8.1 kommt
Oktober-Patchday: Einstieg in Windows 7/8.1 Rollup-Updates
Update-Strategien für Windows 7/8.1 ab November 2016


Since blog readers are often ask, whether they should install the update: For a preview update I always recommend to wait with the installation. Because usually there are issues with such updates – and for Microsoft the preview rollup updates are a test whether there are problems with the rollup update of the following month. Only if a listed fix is relevant for a machine and no serious issues with the preview rollup update are known, I would install the package.

Preview Rollup KB4088881 for Windows 7 SP1

Update KB4088881 is optional (no a security update), and it's offered as a Preview of Monthly Rollup for Windows 7 Service Pack 1 and Windows Server 2008 R2 Service Pack 1, which was released on March 23, 2018. This update contains improvements and fixes that were part of KB4088875 (released March 13, 2018). It also contains the following new quality improvements as a preview of the next monthly rollup update:

  • Improves reliability in the Kernel, and addresses an issue that can cause applications to have unexpected memory contents on multi-processor systems.
  • Addresses issue that decreases the Universal CRT's performance in the _gcvt and _gcvt_s functions.
  • Addresses issue in which the output to a file or pipe was fully buffered in the Universal CRT for the standard error (STDERR) stream.
  • Addresses issue in the Universal CRT by adding the "x" access mode flag to support the fopen()function.
  • Addresses issue with a race condition in the Universal C Runtime (CRT) that occurs when you update the global locale. The issue corrupts the current locale reference count and triggers a double free condition.

The update is offered as an optional Windows Update, but can also be downloaded from the Microsoft Update Catalog. However, I strongly advise against an installation because of the following problem description.

Install requirements

The update is only offered and installed if the antivirus compatibility flag (ALLOW REGKEY) is set in the registry in Windows. To do this, the following subkey within the registry branch HKEY_LOCAL_MACHINE:


is checked. If there is a 32 bit DWORD value cadca5fe-87d3-4b96-b7fb-a231484277cc is present and set to auf 0x00000000, the package will be offered and installed. This flag need be set by the installed virus scanner. Microsoft's antivirus solutions such as Microsoft Security Essentials set the flag.

Avoid this update due to the known issues

For me it is not understandable, why Microsoft has released the PreviewMonthly Rollup at all. Because the following issues are already known.

  • SMB menory leak: After installing this update, SMB servers may leak memory.
  • Blue Screen: A stop error occurs if this update is applied to a 32-bit (x86) machine with Physical Address Extension (PAE) mode disabled.
  • Blue Screen: A stop error occurs on machines that don't support Streaming Single Instructions Multiple Data (SIMD) Extensions 2 (SSE2).
  • Virtual Netzwerk Adapter: After applying this update, a new Ethernet virtual Network Interface Card (vNIC) may be created with default settings in place of the previously existing vNIC, causing network issues. Any custom settings on the previous vNIC are still persisted in the registry but aren't used.

The bugs mentioned above were already present in the previous updates, so they were rolled out with the regular rollup updates of March 13, 2018 and caused a lot of trouble. The issue of lost virtual network adapters was discussed within my blog post Network issues with Updates KB4088875 / KB4088878. A workaround is described in KB article KB3125574 (Convenience Rollup). Microsoft is working on a resolution and is promising an update in an upcoming release since weeks.

Similar articles
Microsoft Patchday Summary March 13, 2018
Security Updates for Windows 7/8.1 (March 13, 2018)
Patchday: Windows 10 Updates (March 13, 2018)
Microsoft Office Patchday (March 13, 2018)
Network issues with Updates KB4088875 / KB4088878
Updates for Windows 8.1/Windows Server 2012/R2 (03/21/2018) 
Windows 10 Updates March 22, 2018
Internet Explorer Update KB4096040 (March 23, 2018)

Cookies helps to fund this blog: Cookie settings

This entry was posted in Update, Windows and tagged , , , . Bookmark the permalink.

One Response to Windows 7: Preview Rollup Update KB4088881 (03/23/2018)

  1. Phil says:

    KB4088881 causes crashes on Windows 2008 R2 Terminal Servers, just like its predecessors KB4088875/8.


Leave a Reply

Your email address will not be published. Required fields are marked *