SQL Server 2025 CU2 released on February 12, 2026. Build 17.0.4015.4, six fixes. I've been running 2025 since RTM, and have been watching things pretty closely — looking for fixes, what to flag for clients, and what's still sitting in the 'known issues' category, pending correction.
Here's the short version.
What's in it
| Area | What was fixed |
|---|---|
| Backup / Restore | StripedVdi tests failing when Sqlvdi.dll wasn't registered on running instances |
| High Availability | AG properties for cluster_type = NONE or EXTERNAL weren't being written to all replicas — only the local one |
| Resource Governor | Potential inaccuracy in tempdb space accounting when Accelerated Database Recovery is enabled |
| Storage Management | Assertion and dump file generated around midnight on New Year's Day during Azure Blob Storage operations |
| Log Management | Nonyielding scheduler dumps in PmmLogAcceptBlock on the AG secondary replica when the persistent log buffer is enabled and the log cache contains primarily tiny log records |
| Replication | Distribution agent using the AG primary replica name instead of the AG listener name when the distributor is in an AG with case-sensitive collation |
The AG properties fix is one I'd have clients look at first — silent misconfiguration on non-primary replicas could cause problems post failover. The tempdb accounting fix matters, too; if you have Accelerated Database Recovery enabled, your tempdb space numbers may have been lying to you.
What isn't in it
Last week I posted about a SESSION_CONTEXT parallel execution bug that's been a 'known issue' since January 2022 — from SQL Server 2019 to 2022, and now 2025. Wrong results. AV dumps. No error message to warn you. CU2 doesn't fix it. There is a workaround, but not without a performance hit.
Getting CU2
Available now from the Microsoft Download Center — no registration required. Be sure to test before you deploy.
More to Read:
KB5075211 — Cumulative Update 2 for SQL Server 2025
Download CU2 — Microsoft Download Center
SESSION_CONTEXT: Three Years, Two Bugs, One Workaround — sqlfingers.com
Thanks for the details.
ReplyDeleteI hope this issue got fixed too(https://learn.microsoft.com/en-us/sql/sql-server/sql-server-2025-known-issues?view=sql-server-ver17#sql-server-might-become-slow-or-unresponsive-after-creating-or-bringing-online-a-large-number-of-databases)
.
MS did earlier released a TF to address the issue but no fix yet in CU 2
Looks like that one's still open. It's tied to a per-database background worker thread from the Persisted Statistics for readable secondary replicas feature -- which is on by default, even when you have no secondary replicas. TF 15608 is the workaround, but it has to be set at startup. Enabling it after the fact won't stop threads already running for databases that are already online. Microsoft has confirmed a fix is planned for a future update. Thanks for flagging it.
Deletehttps://learn.microsoft.com/en-us/sql/sql-server/sql-server-2025-known-issues?view=sql-server-ver17