KB5093421: Cumulative update for SQL Server 2025, CU branch, June 2026. Linked-server error 7416 and incorrect parallel SESSION_CONTEXT results

For: SQL Server instances running parallel vector index builds

• Parallel vector index builds no longer trigger the issue that can exhaust resources and reduce performance.¹
  Addresses an issue during parallel vector index builds that can cause resource exhaustion and performance degradation.

• Changing collation setup no longer unexpectedly blocks mssql-conf on systems with many CPUs.²
  Fixes unexpected blocking of mssql-conf during collation setup on systems with a high CPU count.
• File creation works on file systems that do not support hard links.⁴
  Fixes unexpected file creation failures on file systems that don't support hard links.
• Running sp_executesql in a Linux container with the Korean_Wansung_CI_AS collation no longer triggers Error 17750 (DLL load failure).⁵
  Fixes Error 17750 when running sp_executesql in a Linux container configured with the Korean_Wansung_CI_AS collation.
• Striped backups with 16 or more stripes no longer fail when Transparent Huge Pages is enabled.⁶
  Fixes a possible failure when running striped backups with 16 or more stripes while Transparent Huge Pages (THP) is enabled.
• An index rebuild no longer hits a scheduling issue that can stop the program from responding.⁷
  Fixes a scheduling issue that can prevent a thread from suspending during an index rebuild.
• DDL operations on Change Data Capture tables no longer trigger date conversion errors.⁸
  Fixes date conversion errors triggered by DDL operations on Change Data Capture (CDC) tables.

• Altering a disabled DDL trigger no longer causes a memory access violation.³
  Fixes a memory access violation when altering a disabled DDL trigger.
• A DML operation that inserts a NULL JSON document into a JSON index column no longer encounters the possible failure described in the update.¹³
  Fixes a possible failure during a DML operation that inserts a NULL JSON document into a JSON index column.

For: SQL Server instances

• tempdb space usage accounting is more accurate in the uncommon cases covered by this fix.⁹
  Fixes several issues that can cause tempdb space usage accounting to be inaccurate in uncommon cases.

For: Availability group deployments

• A failed assertion related to thread trace elements no longer occurs on the primary replica of an availability group.¹⁰
  Fixes a failed assertion related to thread trace elements on the primary replica of an availability group.

For: Windows users of SSIS with Encrypt=Strict connections

• SSIS packages can be deployed and run successfully when they connect to SQL Server instances configured with Encrypt=Strict.¹¹
  Fixes SSIS package deployment and execution failures when connecting to instances configured with Encrypt=Strict.

For: SQL Server instances

• The SNI SSL provider handles zero-length TLS records correctly.¹²
  Fixes handling of zero-length TLS records in the SNI SSL provider.

• The Pacemaker resource agent treats a forwarder replica as the local primary for the local availability group orchestrator.¹⁴
  Updates the Pacemaker resource agent's handling of forwarder replicas for the local availability group orchestrator.
• The Windows Failover Cluster log includes more detail when an availability group resource cannot retrieve diagnostic column information.¹⁵
  Adds error information to the Windows Failover Cluster log for this availability group resource DLL condition.

• On Azure SQL Managed Instance, the default FULLTEXT_INDEX_VERSION database setting changes to 2.¹⁶
  Changes the default value of the FULLTEXT_INDEX_VERSION database-scoped configuration to 2 on Azure SQL Managed Instance.

For: Windows users of bcp

• The bcp utility adds bulk import and export support for vector(16) and vector(32), plus options for strict TLS certificate validation. Support for vector(16) becomes functional only after the next ODBC driver release.¹⁷
  Adds -H (HostNameInCertificate) and -J (ServerCertificate) options. vector(16) support in bcp requires the next ODBC driver release to become functional.

For: Windows users saving password-encrypted packages targeting SQL Server 2025

• Password-encrypted SSIS packages targeting SQL Server 2025 use stronger encryption. Packages saved after this update require compatible SSDT and SSMS versions to open; SQL Server 2022 and earlier packages are unaffected.¹⁸
  Upgrades EncryptAllWithPassword and EncryptSensitiveWithPassword to PBKDF2 with SHA-256 and 100,000 iterations. Until compatible SSDT and SSMS versions are released, packages saved after the update, including those created by the Import and Export Wizard, cannot be opened in those tools.