Microsoft has published SQL Server 2025 Cumulative Update 2 (CU2), identified as KB5075211 and build 17.0.4015.4. According to the release notes, this package includes six fixes added after SQL Server 2025 CU1 and updates both the SQL Server engine and Analysis Services components.

The release is broad rather than narrowly focused, covering backup and restore behavior, availability group configuration, Resource Governor accounting, storage management, log handling, and replication.

Known issues

Microsoft documents one known issue in this release:

  • SESSION_CONTEXT in parallel plans — Queries that use the built-in SESSION_CONTEXT function might return incorrect results or generate access violation (AV) dump files when run in parallel query plans. Microsoft says the problem is tied to how SESSION_CONTEXT interacts with parallel execution threads, especially if the session is reset for reuse.

Improvements and fixes

CU2 includes six verified fixes:

  • Backup and restore: fixes a problem that could cause StripedVdi tests to fail when Sqlvdi.dll is not registered on running instances.
  • Availability groups: addresses an issue where, for cluster_type = NONE or EXTERNAL, AG properties existed only on the local replica; the update writes those properties to the AG configuration so all replicas receive the same values.
  • Resource Governor: corrects a potential inaccuracy in tempdb space accounting when accelerated database recovery is enabled for tempdb.
  • Storage management: fixes an issue where an assertion and dump file could be generated around midnight on New Year’s Day during an operation that accesses Azure Blob Storage.
  • Log management: resolves an issue that could trigger nonyielding scheduler dump files in PmmLogAcceptBlock on an AG secondary replica when the persistent log buffer is enabled and the database log cache contains mostly tiny log records.
  • Replication: fixes a case-sensitive collation issue where, if the distributor is part of an AG, the distribution agent used the AG primary replica name instead of the AG listener name.

The update also refreshes the included component versions for SQL Server and Analysis Services as listed in the release notes.

Official source