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SQL Server 2025 CU2 + GDR SQL Server 2025 CU2 + GDR Security update
Patch Tuesday

KB5077466

KB5077466: Security update for SQL Server 2025, CU branch, March 2026. Internal procedure removed; merge replication upgrade flaw fixed

In short

The update removes an internal procedure tied to a potential SQL injection vulnerability and fixes an elevation-of-privilege flaw in merge replication upgrades. It also blocks a specific ALTER USER operation.

Does it affect you? Applies to: SQL Server 2025 on Windows and Linux, all editions. You must already have SQL Server 2025 or a SQL Server 2025 CU through CU2 GDR installed.

Build
17.0.4020.2
Servicing branch
CU
Security
3 fixed
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 2 changes

Replication

  • The merge replication version upgrade process is protected against an elevation-of-privilege vulnerability.1
    Applies to merge replication on Windows.

Security Infrastructure

  • An ALTER USER operation is blocked when its target login is the system Administrator account.2
    Applies on Linux and Windows.

Removal 1 change

Internal System Metadata

  • A potential SQL injection route is removed from the database engine.3
    Removes an internal system stored procedure.

Technical details

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

Data sheet

Released
2026-03-10
Classification
Security Updates
Type
Cumulative update
Servicing branch
CU
Restart
Required
Replaces
KB5075211, KB5078298
Replaced by
KB5083245
VersionBuildChannel
2025 17.0.4020.2 General availability

Security

3 vulnerabilities fixed
3 important
VulnerabilitySeverityCVSS
CVE-2026-21262
Microsoft SQL Server Elevation of Privilege Vulnerability
 Important 8.8
CVE-2026-26115
SQL Server Elevation of Privilege Vulnerability
 Important 8.8
CVE-2026-26116
SQL Server Elevation of Privilege Vulnerability
 Important 8.8

Downloads (Microsoft Update Catalog)

Package 2025
393.8 MB
sqlserver2025-kb5077466-x64.exe Main update · KB5077466 SHA-1: e8d61fa6…bc9f80

Sources

Updated
Cited passages from Microsoft's official notes (3)
  1. 1. Fixes an elevation of privilege vulnerability in the version upgrade process for merge replication. support.microsoft.com
  2. 2. This hotfix blocks the ALTER USER operation if the target login is the system Administrator account. support.microsoft.com
  3. 3. Fixes a potential SQL injection vulnerability by removing an internal system stored procedure. support.microsoft.com
Checked automatically: 8 of 8 checks passed, 3 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 4/5. 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