VMs unbootable with ACPI.sys BSOD

May’s Patch Tuesday for Windows 11 22H2/23H2 bricked virtual machines across Azure, Azure Virtual Desktop, Citrix, and Hyper-V environments. Systems hit BSOD 0xc0000098, reporting ACPI.sys as missing or corrupt, and became completely unbootable — stuck in recovery mode with no way forward. Enterprise cloud infrastructure ground to a halt. Microsoft needed 18 days to ship an emergency out-of-band patch (KB5062170). Nearly three weeks of VMs that couldn’t boot, on the platform Microsoft wants enterprises to trust with their cloud workloads.