SQL Server Security Updates, September 2026: Every Supported Version Patched This Month

What Did Microsoft Release on 8 September 2026?

On 8 September 2026, Microsoft released a coordinated batch of eight security updates covering every currently supported SQL Server version: 2017, 2019, 2022, and 2025. Each version received two packages -- a Cumulative Update (CU) build for customers on the latest CU track, and a General Distribution Release (GDR) build for customers who prefer a minimal-change servicing path. The fixes address vulnerabilities in SQL Server Agent, PolyBase, the VSS Writer, managed backup stored procedures, and the SQL WMI Provider. Because the same vulnerability classes appear across all four versions, this is a broad-surface patch cycle and warrants prompt attention from every SQL Server environment.

Which Versions Are Affected

Use the table below to compare your current build (see the check query further down) against the patched build for your version and branch.

If your build number is lower than the patched build for your version and branch, you are not yet protected by these fixes.

What These Updates Fix

The fixes across the batch cluster into four clear themes.

SQL Server Agent Security and Reliability

This is the most widely shared fix class in the batch -- it appears in every one of the eight packages. Three distinct issues were addressed:

• Task-agent component loading (e.g. KB5442241 / 5442242 / 5442244 / 5442247 / 5442248 / 5442249): When SQL Server Agent loads task-agent components, security validation was insufficient. The fix strengthens that validation so that only legitimate components are accepted.
• Malformed input processing (e.g. KB5456053 / 5456054 / 5456055 / 5456059 / 5456060): Under certain input conditions, SQL Server Agent could encounter reliability and security issues. The fix improves how that input is handled.
• Specific operating conditions (e.g. KB5481777 / 5481779): A separate issue affected the security and reliability of SQL Server Agent under particular runtime conditions. This is fixed in the 2025 and 2022 CU packages.

If you run SQL Server Agent -- and most production instances do -- all three of these apply to you.

SQL WMI Provider Input Handling

Fixed in the CU packages for SQL Server 2025, 2022, and 2017 (e.g. KB5459621 / 5459624 / 5459644 / 5459645, also present in the 2017 GDR). The SQL WMI Provider was processing malformed input incorrectly. The fix ensures malformed input is rejected while preserving existing behaviour for valid input. This matters for any tooling or automation that uses WMI to manage SQL Server instances.

PolyBase Remote Code Execution and Unsafe Deserialisation

Two related PolyBase fixes appear in the SQL Server 2022 GDR, 2019 CU, and 2019 GDR packages:

• Unsafe deserialisation in the PolyBase Engine (e.g. KB5370351 / 5370330 / 5370307): The PolyBase Engine was deserialising data in an unsafe manner, which is a recognised class of vulnerability.
• Raw TCP listener exposure (e.g. KB5406202 / 5406199): A user with administrative permissions could modify PolyBase service command-line parameters to activate a deprecated feature that opened raw TCP listeners for the Data Warehouse Engine and Data Movement Service. The fix prevents PolyBase services from opening those raw TCP listeners when started with modified parameters.

These fixes are relevant only if PolyBase is installed and enabled.

Managed Backup to Azure Stored Procedures

Present across all eight packages (e.g. KB5383374 / 5383381 / 5383447 / 5383448 / 5383449 / 5383450). A vulnerability affects the managed backup stored procedures managed_backup.sp_get_encryption_option and managed_backup.sp_do_backup. Microsoft explicitly calls out that customers using managed backup should apply this update through the standard SQL Server servicing process.

VSS Writer Backup Metadata Validation

Present across most packages (e.g. KB5434227 / 5434229 / 5434230 / 5434231). The SQL Server VSS Writer was not adequately validating backup metadata, meaning malformed or undersized metadata was not being rejected safely. The fix improves that internal validation. This is relevant to any environment using VSS-based backup solutions, including many third-party backup products.

Why You Should Apply These Updates

• SQL Server Agent is hardened against component-loading and input-processing attacks -- relevant to virtually every production SQL Server instance that runs scheduled jobs.
• Managed backup stored procedures are patched -- if you use managed_backup.sp_get_encryption_option or managed_backup.sp_do_backup, you are exposed until you patch.
• PolyBase unsafe deserialisation is resolved -- a recognised vulnerability class that can be exploited if PolyBase is reachable.
• The PolyBase raw TCP listener exposure is closed -- prevents a privileged user from opening unintended network listeners.
• VSS Writer metadata validation is strengthened -- reduces the risk of a malformed backup metadata payload causing unexpected behaviour during VSS-based backup operations.
• The SQL WMI Provider rejects malformed input -- protects management tooling and automation that communicates with SQL Server over WMI.

Are There Known Issues With These Updates?

Two known issues are documented across this batch. Neither is a reason to indefinitely defer patching, but both warrant awareness before you deploy.

Linked Server Queries Using MSDASQL Fail With Error 7416

Affects: All eight packages in this batch.

Trigger: Executing a linked server query where the linked server uses the MSDASQL (Microsoft OLE DB Provider for ODBC Drivers) provider.

Symptom: The query fails with error 7416.

Recommendation: If your environment uses MSDASQL-based linked servers, test this scenario in a non-production environment before rolling out to production. Check the relevant KB article for any workaround Microsoft has published by the time you patch. This issue alone should not delay patching for environments that do not use MSDASQL linked servers.

Access Violation When Querying sys.dm_exec_requests During Database Recovery

Affects: SQL Server 2025 RTM CU8 (KB5122769) and SQL Server 2022 RTM CU26 (KB5122768) only.

Trigger: Querying sys.dm_exec_requests while a database is in the recovery phase (for example, immediately after a service restart or failover).

Symptom: An access violation occurs.

Recommendation: For environments where monitoring tools or custom scripts poll sys.dm_exec_requests continuously, be aware that a restart or failover window carries a small additional risk with these two CU builds. This is unlikely to affect most environments in practice, but it is worth noting if you have aggressive monitoring that runs during startup.

Does This Affect You? How to Check

Check Your Current Build

SELECT
    SERVERPROPERTY('ProductVersion') AS Build,
    SERVERPROPERTY('ProductLevel')   AS Level,
    SERVERPROPERTY('ProductUpdateLevel') AS CULevel;

Compare the returned build number against the patched builds in the table above.

Check Whether SQL Server Agent Is Running

SELECT
    servicename,
    status_desc,
    startup_type_desc
FROM sys.dm_server_services
WHERE servicename LIKE 'SQL Server Agent%';

If the Agent service is present and running, the Agent-related fixes in this batch apply to you.

Check Whether Managed Backup Is Configured

SELECT name
FROM sys.databases
WHERE is_managed_backup_enabled = 1;

If any rows are returned, the managed backup stored procedure vulnerability is directly relevant to your environment.

Check Whether PolyBase Is Installed and Enabled

SELECT SERVERPROPERTY('IsPolyBaseInstalled') AS PolyBaseInstalled;

A return value of 1 means PolyBase is installed. To confirm it is also enabled, check whether the PolyBase Engine and PolyBase Data Movement services are running using sys.dm_server_services as shown above.

Check for MSDASQL-Based Linked Servers (Known Issue)

SELECT
    name        AS LinkedServerName,
    provider    AS Provider,
    data_source AS DataSource
FROM sys.servers
WHERE is_linked = 1
  AND provider = 'MSDASQL';

If any rows are returned, test the known error 7416 issue in a non-production environment before patching production.

How to Apply

1. Check your current build using the query above and confirm which package you need.
2. Download from the Microsoft Download Center or Microsoft Update Catalog using the KB links in the table above.
3. Apply to a non-production environment first and run your standard regression and smoke tests, including any linked server queries if MSDASQL is in use.
4. Take a full backup of all user databases and the system databases before patching production.
5. Plan for a service restart -- all SQL Server patching requires a restart of the SQL Server service.
6. Verify the build number after patching by re-running the build check query and confirming it matches the patched build in the table.
7. For Always On Availability Groups, patch secondary replicas first, fail over, then patch the former primary to minimise downtime.

What If You Are on an Unsupported Version?

SQL Server 2016 reached end of extended support in July 2026. SQL Server 2014 and earlier have been out of support for longer still. None of these versions receive the fixes described in this article. If your environment is running an unsupported version, the vulnerabilities patched here -- including the SQL Server Agent issues, the PolyBase deserialisation flaw, and the managed backup vulnerability -- remain open with no remediation path from Microsoft. Upgrading to a supported version is the only way to close these gaps.

Key Takeaways

• Microsoft patched all four currently supported SQL Server versions (2017, 2019, 2022, 2025) simultaneously on 8 September 2026, with both CU and GDR builds for each.
• The most broadly shared fixes harden SQL Server Agent against security and reliability issues -- this affects nearly every production SQL Server environment.
• Managed backup to Azure, PolyBase, the VSS Writer, and the SQL WMI Provider all received targeted security fixes.
• A known issue with MSDASQL-based linked servers (error 7416) affects all eight packages and should be tested before production deployment if applicable.
• Unsupported versions receive none of these fixes and represent an increasing security liability.

DBA Services Recommendation

All DBA Services managed clients have these updates scheduled for non-production deployment this week, with production rollout following successful validation. If you manage your own SQL Server environment and would like help assessing your exposure, planning a patching schedule, or moving off an unsupported version, get in touch with the DBA Services team.