In this case, CU means cumulative update for Windows 10. Servicing stack updates, also known as SSUs, pave the way for successful CU installs. As the MS Servicing stack updates web page explains, these updates “provide fixes to the servicing stack, the component that installs Windows updates.” In essence, that means SSU updates make sure that any potential gotchas that might prevent the CU from installing correctly are addressed before the gotchas can bite. This quote explains what’s up. “If you don’t install the latest servicing stack update, there’s a risk that your device can’t be updated with the latest Microsoft security fixes.” Hence also the title: Win10 Servicing Stack updates support CUs. Got that?
How Is It That Win10 Servicing Stack Updates Support CUs?
SSUs are supposed to be released at the same time that monthly quality updates and CUs are released. Sometimes, an SSU may go out on its own to address issues that affect systems installing a monthly update of some kind. Starting November 2018, new SSUs are classifed as Security updates with a “Criticial” severity rating. You can look at SSUs as a kind of just-in-time update that prepares systems to accept and work with other updates. It’s all good, right?
There’s just one little gotcha when it comes to SSUs. They don’t appear in the Windows 10 Update History. For the record, the most recent SSU (dated 12/4/2018) is KB4470788. Note this snippet from my Lenovo T520 laptop, onto which I installed the latest updates yesterday.
Note the absence of an SSU entry in the preceding list. Nothing is numbered 4470788. What’s up with that?
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If There’s No SSU Visible, Is It Really There?
Oh, it’s there all right. MS chooses not to show it in its Update History list for some odd reason or another. If you use the DISM /Online /Get-Packages command, it shows up near the end of that listing, like this:
The red arrow flags the KB4470788 entry, and shows it appears as a Security Update as claimed earlier. Perforce it’s installed before the CU (RollupFix item at end of list).
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I learned by trial and error on Wednesday/Thursday that sometimes the SSU may NOT precede a CU. If that should happen, this may manifest in WU failing to offer the CU. I noticed that four of the five machines I have running 17763.167 got the offer, but the fifth did not. On a whim, I downloaded and installed the SSU from the Microsoft Update Catalog. Immediately thereafter, WU offered the missing CU (KB4469342). I’m not sure why this happened, but I was glad to find a way to address the situation. Should you ever find yourself in the same boat, this technique might also work for you. Find the Servicing Satck Update KB article numbers in Microsoft Security Advisory ADV990001 Latest Servicing Stack Updates. Then you can use that info to grab what you need from the Update Catalog.