Some servers were unable to install the update properly, while others became stuck in continuous restart loops
Microsoft has released emergency software updates to fix issues that disrupted some Windows Server systems following its latest monthly security patches.
The problems emerged after April’s Patch Tuesday rollout, a regular cycle of updates designed to address security vulnerabilities.
Many system admins reported that certain servers failed to install the update correctly, while others entered repeated restart loops.
The failures were linked in part to crashes in a critical Windows process known as the Local Security Authority Subsystem Service (LSASS), which handles authentication and security policies.
Systems configured as domain controllers – essential for managing network logins in organisations – were particularly affected.
Microsoft acknowledged that a limited number of devices running Windows Server 2025 encountered installation errors, often displaying error code 800F0983.
The company said it had been monitoring diagnostic reports before issuing the out-of-band (OOB) fixes.
In a service alert, the company confirmed that the issues could also arise when setting up new domain controllers, especially if authentication requests were processed early during system startup.
“A limited number of affected servers might experience an installation failure accompanied by the error code 800F0983,” it said.
Emergency patches released
Microsoft has now rolled out emergency updates for the following affected Windows Server versions:
- Windows Server 2025: KB5091157 (OS Build 26100.32698) Out-of-band
- Windows Server, version 23H2: KB5091571 (OS Build 25398.2276) Out-of-band
- Windows Server 2022: KB5091575 (OS Build 20348.5024) Out-of-band
- Windows Server 2019: KB5091573 (OS Build 17763.8647) Out-of-band
- Windows Server 2016: KB5091572 (OS Build 14393.9062) Out-of-band
- Windows Server 2025 Datacenter: Azure Edition: Hotpatch KB5091470 (OS Build 26100.32704) Out-of-band
- Windows Server 2022 Datacenter: Azure Edition: Hotpatch KB5091576 (OS Build 20348.5029) Out-of-band
The company says the update for Windows Server 2025 resolves both the installation failure and the restart loop problem, while patches for earlier versions focus on preventing the reboot issue.
Some Windows Server 2025 devices might unexpectedly enter BitLocker recovery mode after installing the earlier April update, prompting users to input encryption keys. However, such scenarios are typically limited to enterprise-managed systems rather than home users, according to the company.
Update concerns
The incident is the latest in a series of disruptions linked to Microsoft’s monthly updates. In recent months, emergency patches have been issued to fix authentication failures in Windows 11, Bluetooth connectivity problems, and other enterprise-related bugs.
Earlier this year, January’s Patch Tuesday triggered widespread complaints, including broken remote desktop access and application crashes, leading to renewed scrutiny of update reliability.
In March, Microsoft released an emergency update to address a Windows 11 glitch that disrupted authentication across several apps, including Teams Free, OneDrive and Copilot.
The problem stemmed from the 10 March Patch Tuesday update (KB5079473) for Windows 11 versions 24H2 and 25H2.
Last week, the company resolved a long-running issue affecting Windows Server 2019 and 2022 systems that were unexpectedly upgrading to newer versions without user intent.
Microsoft says it is working to improve the stability of its update process.
In a message to users, Windows chief Pavan Davuluri acknowledged concerns and pledged higher standards.
“Thank you for holding us to a high standard,” he said.
“Windows is as much yours as it is ours. We’re committed to strengthening its foundation and delivering innovation where it matters, for you.”
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