Microsoft has confirmed that Windows updates released since the October 2026 Patch Tuesday are causing SQL Server performance and stability issues across multiple versions.
The problems manifest as slower query execution, reduced transaction throughput, and occasional service crashes that were not observed before the updates. Database administrators have noted increased CPU and memory pressure even under moderate workloads, pointing to changes in how the Windows kernel handles memory allocation and disk I/O operations used by SQL Server.
Microsoft engineers have identified the regression in core operating system components introduced after the October cumulative update cycle. The company is currently testing targeted fixes and has published interim guidance recommending specific registry adjustments and service configuration changes to mitigate the impact until a permanent resolution is available.
Organizations running production SQL Server instances are advised to monitor performance counters closely and consider delaying further non-security updates until the issue is resolved. Microsoft continues to collect telemetry data from affected systems to refine its diagnosis and accelerate delivery of a corrective patch.
