Patch tracker / KB5091158
KB5091158: Microsoft SQL Server 2025 for x64-base Security Update (May 2026)
KB5091158 is a High security update for Microsoft SQL Server 2025 for x64-base, released 2026-05-12. It closes 1 CVE with a maximum CVSS of 8.8. It is the 37th largest of the 61 updates Microsoft shipped that month, by CVEs closed.
Update summary
Fixes 1 CVE. Most severe CVSS 8.8 (High). EPSS exploit probability up to <1%. Among the lower half of tracked Microsoft updates by EPSS exploit probability.
Microsoft documents 1 known issue with this update.
- Linked server queries that use MSDASQL fail with error 7416
KB5091158 patches CVE-2026-40370 across three SQL Server generations at once: SQL Server 2025 (CU4), 2022 (CU24), and the older 2017 GDR track. It rates High at CVSS 8.8, which points to a network-reachable flaw that can escalate privileges or execute code once an attacker has some access to the instance. Anyone still running SQL Server 2017 should note the GDR-only fix, meaning no CU option exists on that version.
Do this: Identify which SQL Server build each instance runs and apply the matching CU (2025 CU4, 2022 CU24) or the 2017 GDR update from KB5091158.
AI-generated from public data, 2026-07-21. Verify against the vendor advisory before acting.
Senserva AI Opinion and rich prompt for KB5091158
Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.
Full tracking and change history for KB5091158
- Released
- 2026-05-12
- Last changed
- 2026-05-12
- Changes tracked
- 1
Senserva began recording day-to-day change history on 2026-07-07, and refreshes it several times a day. Release dates are historical where Microsoft publishes them; revision history is tracked from that date forward, so it does not include changes made before then.
Check if KB5091158 is installed
Elevated PowerShell. No output means it is not installed.
Known issues, from Microsoft
Quoted from Microsoft's support article for KB5091158 (checked 2026-08-06). Verify against the article before acting.
Linked server queries that use MSDASQL fail with error 7416
Linked server queries that use the MSDASQL (OLE DB Provider for ODBC Drivers) provider and specify a provider string (@ provstr ) fail and return the following error message:
Msg 7416, Level 16
Access to the remote server is denied because no login-mapping exists.
A stricter connection validation check in the Database Engine can reject connections for certain linked server configurations that use the MSDASQL provider, even if earlier builds allowed those connections.
For more information and workarounds, see Linked server queries that use MSDASQL fail with error 7416.
CVEs fixed by this update
Sorted exploited-first, then by CVSS. Every CVE links to its Senserva page with the full risk facts, references, and a ready-to-paste AI prompt.
| CVE | Severity | CVSS | EPSS | Exploited |
|---|---|---|---|---|
| CVE-2026-40370 | High | 8.8 | <1% | No |
Scope and sources
- Affected products
- Also released in May 2026
KB5002863
9 CVEs · High · exploitedKB5002868
9 CVEs · High · exploitedKB5002870
9 CVEs · High · exploitedKB5094139
1 CVE · High · exploitedKB5094140
1 CVE · High · exploitedKB5094142
1 CVE · High · exploitedKB5094144
1 CVE · High · exploitedKB5078943
3 CVEs · CriticalThe full month, summarized: Microsoft Patch Tuesday.
- Authoritative references
See this and every Microsoft update ranked by real-world risk on the Microsoft Patch Tracker.