Microsoft: Recent Windows updates cause SQL Server performance issues
Microsoft confirms Windows updates since Oct 2026 cause SQL Server performance issues.
Microsoft has confirmed that Windows updates released since the October 2026 Patch Tuesday are causing performance and stability issues for SQL Server. The problem stems from server queries that leave connections open after completion, leading to an accumulation of connections that degrade server performance. This issue affects SQL Server linked server queries using OLE DB providers to connect to external databases like Oracle and PostgreSQL.
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The lesson from this incident
Full lessonMicrosoft's October 2026 Patch Tuesday updates introduced a regression that causes SQL Server linked server queries to leave database connections open after completion, gradually exhausting connection pools and degrading server performance. This highlights a critical risk in patch management: even vendor-supplied updates from trusted sources can introduce unintended instability in complex, interdependent enterprise environments. Organizations relying on SQL Server linked queries to Oracle, PostgreSQL, or other external databases faced potential outages without warning. It matters because patch-induced regressions can be just as disruptive as the vulnerabilities the patches were meant to fix, and without proper testing pipelines or rollback plans, recovery is slow and painful.
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