Microsoft has released SQL Server 2022 Cumulative Update 26 (CU26), also tracked as KB5093420 and build 16.0.4265.3. According to Microsoft, this cumulative update includes 12 fixes after SQL Server 2022 CU25 and updates both the Database Engine and Analysis Services components.
For DBAs and developers, the main takeaway is that CU26 is a broad servicing update. It touches availability groups, query processing, maintenance plans, programmability, and storage-related code paths, while also documenting two known issues that readers should keep in mind.
Known issues
Microsoft lists two known issues in CU26:
- SESSION_CONTEXT in parallel plans can return incorrect results or trigger access violation dump files when queries run in parallel plans, especially if the session is reset for reuse.
- Linked server queries using MSDASQL can fail with Msg 7416 when a provider string (
@provstr) is specified, because stricter connection validation may reject some linked server configurations.
Microsoft notes that more information is available in the linked issue entries. Removal of an issue from the source would not, by itself, prove that it has been resolved.
Improvements and fixes
CU26 contains 12 verified fixes, grouped below by area:
High availability and disaster recovery
Microsoft added more detailed Windows Server Failover Cluster log information when the availability group resource DLL cannot retrieve diagnostic column data. CU26 also adds support for removing an IP address from an availability group listener with ALTER AVAILABILITY GROUP ... MODIFY LISTENER ... REMOVE IP.
Another availability group fix addresses intermittent failures where monitoring queries that use sys.dm_exec_requests or sys.sysprocesses return error 976 or 978 on a secondary replica.
Query execution and statistics
Several fixes target query behavior and optimization:
- The new cardinality estimator’s interpolation calculation was adjusted for very large values to avoid an ALTER INDEX operation choosing a serial plan.
- Incremental statistics sampling is adjusted when the last sampling rate was 100 percent and many new rows have been inserted.
Maintenance and storage access
Microsoft fixed a maintenance plan issue where an index rebuild plan could stop responding because of a long-running query.
In storage-related areas, CU26 improves memory management during query compilation for columnstore indexes, reducing compilation time, and fixes a nonyielding scheduler condition that could occur when sys.dm_db_index_operational_stats iterates through a large number of cached heaps or B-trees.
Programmability and engine stability
CU26 fixes an access violation that could occur when running ALTER PARTITION FUNCTION ... SPLIT RANGE against a partition function used by a table with an identity column referenced by a clustered index on a schema-bound view.
It also addresses a nonyielding scheduler condition that could happen when SQL Server writes certain errors to the error log.
Security and platform maintenance
Microsoft says CU26 fixes a SQL injection vulnerability in sys.sp_MSforeachdb that could allow an authorized attacker to elevate privileges over a network.
The update also removes the deprecated RSA32Lib cryptographic library as part of ongoing cryptography modernization.
Scope at a glance
The documented fixes cover:
- Availability group diagnostics and listener management
- Query optimizer and statistics behavior
- Maintenance plan responsiveness
- Programmability stability
- Storage and compilation performance
- Security hardening and cryptography cleanup
If you manage SQL Server 2022 environments, CU26 is worth reviewing for the specific engine areas it touches, especially if you rely on availability groups, maintenance plans, or the affected DMVs and built-in procedures.