Microsoft: Recent Windows updates cause SQL Server performance issues
Microsoft said that Windows updates released since the October 2026 Patch Tuesday are causing SQL Server performance and stability issues.
Microsoft said that Windows updates released since the October 2026 Patch Tuesday are causing SQL Server performance and stability issues.
As detailed in a Windows release health dashboard update on Wednesday, this is caused by server queries that leave connections open after the queries complete.
These connections accumulate instead of closing, degrading server performance over time.
It also added that admins may be able to manually close connections left open due to this bug or restart the SQL service to temporarily address stability and performance issues, but this can also kill active queries and may not fully address the issue, as it will resurface again after some time.
Microsoft says the issues impact both client (Windows 10 and Windows 11) and server (Windows Server 2012 and later) systems and will be fixed with an out-of-band Windows update to be released over the next few days.
Yesterday, the company also confirmed reports that the November 2026 security updates are failing to deploy on Windows 11 systems where the October preview update has been installed, with affected users seeing 0x80070306, 0x800f0989, or 0x800f0993 error codes.
This issue affects SQL Server linked server queries that use OLE DB providers to connect to external databases, and oracle and PostgreSQL connections are among those known to be affected, Microsoft explained.
While it works to resolve the bug, Microsoft said IT administrators can reach out to Microsoft Support for Business for a mitigation that can address the issue until a fix is available.
The bug affects SQL Server when the Lock Pages in Memory (LPIM) Windows policy is enabled and may cause SQL Server crash dumps, SQL Server services to stop or restart unexpectedly, failures during database maintenance operations, memory corruption errors, and access violation exceptions (with 0xC0000005 error codes).
In September, Microsoft also shared a temporary workaround for SQL Server crashes on some Windows Server 2025 due to recent memory management changes.
What happened
Microsoft said that Windows updates released since the October 2026 Patch Tuesday are causing SQL Server performance and stability issues.
As detailed in a Windows release health dashboard update on Wednesday, this is caused by server queries that leave connections open after the queries complete.
These connections accumulate instead of closing, degrading server performance over time.
What changed
It also added that admins may be able to manually close connections left open due to this bug or restart the SQL service to temporarily address stability and performance issues, but this can also kill active queries and may not fully address the issue, as it will resurface again after some time.
Microsoft says the issues impact both client (Windows 10 and Windows 11) and server (Windows Server 2012 and later) systems and will be fixed with an out-of-band Windows update to be released over the next few days.
Yesterday, the company also confirmed reports that the November 2026 security updates are failing to deploy on Windows 11 systems where the October preview update has been installed, with affected users seeing 0x80070306, 0x800f0989, or 0x800f0993 error codes.
Who is affected
This issue affects SQL Server linked server queries that use OLE DB providers to connect to external databases, and oracle and PostgreSQL connections are among those known to be affected, Microsoft explained.
Why it matters
While it works to resolve the bug, Microsoft said IT administrators can reach out to Microsoft Support for Business for a mitigation that can address the issue until a fix is available.
The bug affects SQL Server when the Lock Pages in Memory (LPIM) Windows policy is enabled and may cause SQL Server crash dumps, SQL Server services to stop or restart unexpectedly, failures during database maintenance operations, memory corruption errors, and access violation exceptions (with 0xC0000005 error codes).
Technical details
In September, Microsoft also shared a temporary workaround for SQL Server crashes on some Windows Server 2025 due to recent memory management changes.
What to watch next
Watch for additional victim details, indicators of compromise and follow-on exploitation reports.
Watch for revised vendor guidance, fixed versions and mitigation updates.