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SQL Server 2025 CU1 SQL Server 2025 CU1 Cumulative update

KB5078298

KB5078298: Cumulative update for SQL Server 2025, CU branch, January 2026. Database Mail restored; parallel SESSION_CONTEXT issue remains

In short

This CU restores Database Mail functionality broken by the initial CU1 release and includes 16 fixes. Queries using SESSION_CONTEXT in parallel plans can still return incorrect results or cause access violation dump files.

Does it affect you? Applies to: This update applies to SQL Server 2025 on Windows and Linux. It updates SQL Server to build 17.0.4006.2 and Analysis Services to build 17.0.25.223.

Build
17.0.4006.2
Servicing branch
CU
Restart
Required

For servers on the CU branch: they install cumulative updates, which also bring fixes beyond security. Servers on the GDR branch (security fixes only) get a separate update. Which branch am I on?

What changes

Fixes 11 changes

Programmability

For: SQL Server deployments

  • DBCC CHECKDB no longer hangs or returns an exception in the specified computed-column setup when trace flag 176 is enabled.1
    Fixes DBCC CHECKDB with EXTENDED_LOGICAL_CHECKS when a table has both persisted and non-persisted computed columns and trace flag 176 is enabled.

SQL Connectivity

For: Windows

  • SQLCMD no longer crashes when you use the -N switch in a :CONNECT command.2

Linux

4 items
  • CPU usage metrics reported for SQL Server on Linux are corrected.3
    Corrects metrics in the sys.dm_os_ring_buffers DMV.
  • SQL Server on Linux no longer fails when it reads an invalid ID type from the Domain Controller.4
  • Active Directory logins work when the keytab is updated after the privileged user password is rotated.5
  • VDI restore operations in Linux containers no longer unexpectedly run out of memory when a Linux cgroup limits memory.8

SQL Server Configuration Manager

For: Windows

  • SQL Server Configuration Manager no longer stops responding when importing a certificate.6

LibOS

For: SQL Server on Linux

  • During the daylight-saving-time fall-back, timestamps no longer get an incorrect time zone.7
    Fixes timestamps that might have an incorrect time zone during a Daylight Saving Time "Fall Back" on Linux.

Resource Governor

For: SQL Server deployments using the specified trace flags

  • A trace-flag configuration that might cause the SQL Server process to stop responding is fixed.9
    Addresses the configuration in which trace flag 15918 is enabled by DBCC TRACEON while startup trace flag 15923 is enabled.

Search

For: SQL Server deployments

  • Creating a full-text index on a .docx file produces correct results when a paragraph begins with a hyperlink and the preceding paragraph has no trailing whitespace.10

Database Mail

  • Database Mail functionality is restored for users affected by the initial CU1 release, KB5074901.11
    If the initial release is installed, install the current CU1 version over it or uninstall the initial release. Messages queued through Database Mail while the initial release was installed aren't automatically resent.

Improvements 3 changes

Security Infrastructure

For: SQL Server deployments

  • Only sysadmins can invoke dbcc stackdump to create a dump file.12

SQL OS

2 items
  • The error log now includes an information message when the deprecated lightweight pooling configuration is enabled.13
  • The sys.fn_xe_file_target_read_file() function can read system_health event session data in Azure SQL Managed Instance.14

New features 2 changes

Linux

For: SQL Server on Linux containers

  • SQL Server 2025 can be registered on Linux containers by setting MSSQL_PID to StandardDeveloper or EnterpriseDeveloper.15

High Availability and Disaster Recovery

  • Contained Availability Group users can create or restore a database through a listener without connecting to the SQL instance.16
    Enables creating or restoring a database by using a listener for Container Availability Group Connection.

Removal 1 change

Search

For: SQL Server on Linux

  • On Linux, full-text system DMVs no longer report .rtf as a supported document type.17

Known issues

  1. Open Affects: Everyone

    Incorrect behavior of SESSION_CONTEXT in parallel plans

    Queries using SESSION_CONTEXT in parallel query plans might return incorrect results or trigger access violation (AV) dump files, particularly if the session is reset for reuse.18

    Workaround status No workaround yet

    Microsoft has not published a manual workaround for this issue yet. Monitor release health until a resolving update is available.

Technical details

Data sheet · Security · Downloads · Components Click to collapse or expand

Data sheet

Released
2026-01-29
Classification
Updates
Type
Cumulative update
Servicing branch
CU
Restart
Required
Replaced by
KB5075211
VersionBuildChannel
2025 17.0.4006.2 General availability

Security

No vulnerabilities are listed for this update.

Downloads (Microsoft Update Catalog)

Package 2025
392.2 MB
sqlserver2025-kb5078298-x64.exe Main update · KB5078298 SHA-1: 7e9a2e1a…961ed3

Sources

Updated
Cited passages from Microsoft's official notes (18)
  1. 1. Fixes an issue in which DBCC CHECKDB with EXTENDED_LOGICAL_CHECKS stops responding and returns an exception if there are both persisted and non-persisted computed columns in a table while trace flag 176 is enabled. learn.microsoft.com
  2. 2. Fixes an issue that causes SQLCMD to crash when you use the -N switch in a :CONNECT command. learn.microsoft.com
  3. 3. Fixes incorrect CPU usage metrics in sys.dm_os_ring_buffers DMV for SQL Server on Linux. learn.microsoft.com
  4. 4. Fixes an issue that causes SQL Server on Linux to fail when it reads an invalid ID type from the Domain Controller. learn.microsoft.com
  5. 5. Fixed an issue in SQL Server on Linux that prevents Active Directory logins from working when the keytab is updated after the privileged user password is rotated. learn.microsoft.com
  6. 6. Fixes an issue that causes SQL Server Configuration Manager (SSCM) to stop responding when importing a certificate. learn.microsoft.com
  7. 7. Fixes an issue during a Daylight Saving Time "Fall Back" in which timestamps may have an incorrect time zone. learn.microsoft.com
  8. 8. Fixes an issue in which VDI restore operations on Linux containers can run out of memory unexpectedly if memory is limited by a Linux cgroup. learn.microsoft.com
  9. 9. If traceflag 15918 is enabled by using DBCC TRACEON on a SQL Server instance by having startup traceflag 15923 enabled, this configuration might cause the SQL Server process to stop responding. learn.microsoft.com
  10. 10. Fixes an issue in which creating a full-text index on a .docx file produced incorrect results if a paragraph began with a hyperlink and the preceding paragraph did not contain trailing whitespace. learn.microsoft.com
  11. 11. This issue is resolved in the current version of this cumulative update (KB5078298). learn.microsoft.com
  12. 12. Restricts the privilege for dbcc stackdump so that only the sysadmin can invoke the dump file. learn.microsoft.com
  13. 13. Adds an information message in the error log if the deprecated lightweight pooling configuration is enabled. learn.microsoft.com
  14. 14. Allows the use of sys.fn_xe_file_target_read_file() function to read the system_health event session data in Azure SQL Managed Instance. learn.microsoft.com
  15. 15. SQL Server 2025 can now be registered on Linux containers by setting the MSSQL_PID environment variable to StandardDeveloper or EnterpriseDeveloper. learn.microsoft.com
  16. 16. Enables creating or restoring the database by using a listener for Container Availability Group Connection. This feature lets Contained AG users create and restore the database without a connection to the SQL instance. learn.microsoft.com
  17. 17. Removes .rtf from full-text system DMVs on the Linux platform. This document type was previously incorrectly reported as supported. learn.microsoft.com
  18. 18. Queries that use the built-in SESSION_CONTEXT function might return incorrect results or trigger access violation (AV) dump files when run in parallel query plans. learn.microsoft.com
Checked automatically: 8 of 8 checks passed, 18 quoted passages · compared with Microsoft's page on Sep 26, 2026
  • Quotes found in the official pages: passed
  • Numbers found in the sources: passed
  • Vulnerabilities from the dossier only: passed
  • Links to allowed domains only: passed
  • Every official change covered: passed
  • Readable plain text: passed
  • Changes confirmed by the file list: passed
  • Sources agree: passed

A second AI read the text against the sources: correctness 5/5, clarity 4/5, completeness 5/5. How we work

Published by The Update Bureau. Written with AI from Microsoft's own documents, checked by rules and a second AI. How we work · Report a mistake