Emergency Windows Server updates issued by Microsoft

Out-of-band (OOB) is an upgrade that has been made available by Microsoft to address problems with Windows Server systems following the installation of the April 2026 security updates.

Some administrators had encountered issues when deploying the KB5082063 security update on Windows Server 2025 machines, as Microsoft acknowledged last week.

Additionally, some Windows servers with domain controller responsibilities are experiencing a restart loop as a result of this month’s Patch Tuesday cumulative updates because the Local Security Authority Subsystem Service (LSASS) is crashing.

Additionally, Microsoft cautioned that if the server performs authentication requests relatively early during startup, this problem could also arise while configuring new domain controllers (or even on existing ones).

Microsoft has issued emergency updates for the following impacted Windows Server versions in order to resolve these two known issues: 

• Windows Server 2016: KB5091572 (OS Build 14393.9062), this fixes Domain Controller reboots
• Windows Server 2019: KB5091573 (OS Build 17763.8647) this fixes Domain Controller reboots
• Windows Server 2022: KB5091575 (OS Build 20348.5024) fixes Domain Controller reboots
• Windows Server 2022 Datacenter: Azure Edition: Hotpatch KB5091576 (OS Build 20348.5029) fixes these domain controller reboots
• Windows Server 2025: KB5091157 (OS Build 26100.32698) this fixes both DC reboots & Install failures
• Windows Server 2025 Datacenter: Azure Edition: Hotpatch KB5091470 (OS Build 26100.32704) this fixes both DC reboots & Install failures
• Windows Server, version 23H2: KB5091571 (OS Build 25398.2276) fixes these domain controller reboots

Microsoft further clarified that the Windows Server 2025 OOB update (KB5091157) fixes both installation failure and domain controller restart issues, while OOB updates for other supported versions only address the restart issue. 

Additionally, Microsoft warned that after downloading the KB5082063 security update, some Windows Server 2025 systems will boot into BitLocker recovery, requiring a recovery key, and a flaw present since September 2024 was finally fixed last week, causing Windows Server 2019 and 2022 machines to unexpectedly upgrade to Windows Server 2025. 

Also, Microsoft stated that it has been releasing emergency updates since the start of the year to fix some of its features, such as its Bluetooth visibility fault, and patch RRAS security flaws affecting Windows 11 Enterprise with hotpatch support, and the March 2026 non-security preview update was impacted by two out-of-band upgrades that resolved Microsoft account sign-in issues and update installation problems.