Microsoft Acknowledges SQL Server Connection Leakage After October Update
A recent update causes linked server queries to leave connections open, degrading performance.
1October Update Causes Instability
Microsoft confirmed that the October 13 update, identified as KB5126646, introduced a critical defect in SQL Server. The issue specifically impacts linked server queries utilizing OLE DB providers. Instead of closing connections after data retrieval, the system keeps them open, leading to an accumulation of idle sessions that degrade overall server performance.
2Impact on External Databases
The technical glitch affects connections to various external databases, with PostgreSQL and Oracle explicitly cited as examples. Administrators have reported a suspicious surge in open connections, which directly correlates with the installation of the latest update. This behavior prevents the server from efficiently managing resources, causing significant latency during prolonged operational periods.
3Manual Mitigation and Risks
Microsoft suggests that administrators can manually close idle connections or restart the SQL service to restore temporary stability. However, these actions carry inherent risks, as they may inadvertently interrupt active queries or ongoing transactions. Furthermore, the company warns that the connection leakage problem is likely to resurface after a period of operation.
4Scope of Affected Systems
The defect is widespread, impacting nearly every version of Windows except Windows 11 26H2. Affected platforms include Windows 10 versions starting from 1809 and LTSC 2019. Additionally, the issue spans Windows Server releases ranging from 2012 up to the 2025 edition, creating a broad maintenance challenge for IT departments managing legacy and modern infrastructure.
5Path to Permanent Resolution
While a mitigation strategy is currently available exclusively through Microsoft support for business customers, a general fix is pending. The company indicated that an out-of-band update is expected to be released within the next few days. Until then, administrators must rely on manual workarounds to maintain system performance and prevent complete service failure.
6Historical Context of Updates
This incident follows a pattern of recent update-related complications for Microsoft server products. Notably, the October 2026 Windows Server update previously caused instability for Exchange Servers. That specific issue required either a manual Registry edit or a subsequent November update to resolve, highlighting ongoing challenges with the company's monthly patch deployment cycle.
7Operational Burden for Admins
For many system administrators, the necessity of restarting services to address memory or connection leaks is a familiar, albeit frustrating, routine. While bouncing a SQL Server provides a temporary reprieve, it is considered a suboptimal solution. It serves as an unplanned failover test but fails to address the underlying architectural flaw introduced by the update.
8Future Outlook and Monitoring
Organizations relying on linked servers for data integration should monitor their connection counts closely until the patch arrives. The recurrence of these stability issues underscores the importance of rigorous testing before deploying updates in production environments. Future stability depends on Microsoft delivering a robust, permanent fix that does not disrupt critical business data workflows.