In another episode of “Quality Control Took a Vacation”, Microsoft enabled the installation of two hotfixes during its traditional Patch Tuesday for two versions of Windows 10 (1607 and 1703) and Windows Server 2016 that knocked out thousands of systems, leaving them stuck in reboot loops and blue screens. The problem isn't inside the patches but in the distribution method, and although it mainly affects enterprise machines, the incident represents another crack in the update structure.
Last Tuesday, October 10, Microsoft released two new hotfixes. The first is KB4041676 for Windows 10 1703 (Creators Update), and the second is KB4041691, compatible with Windows 10 version 1607 (Anniversary Update) and Windows Server 2016. The patches apply a good number of bug fixes and security updates in different modules of the operating system. Good news as far as the eye can see... except that it makes computers crash against the guardrail. And that was exactly what happened: thousands of users around the world who received the hotfixes were greeted by blue screens and terminals stuck in a classic reboot loop.
An important detail about the incident is that the most affected environment was the enterprise one, with computers managed via Windows Server Update Services (WSUS) and System Center Configuration Manager (SCCM). The error that appears on the BSOD is “INACCESSIBLE_BOOT_DEVICE”, and the operating system tries to start an automatic repair but never completes the task. What happened? At first it was believed there was a problem inside the hotfixes, however, over the hours it was verified that there was a distribution error: Microsoft published in WSUS and SCCM two types of patches at the same time: the cumulative (which contains previous hotfixes) and the differential or “Delta,” much smaller. In other words, “double hotfix” broke everything.
Microsoft published special documents with repair details for affected systems here and here. The exact steps depend on the type of scenario the user must face, but it's not something pretty. We also found guides on Reddit and other portals. We hope the situation stabilizes soon.
