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.NET Framework 3.5 / 4.8 .NET Framework 3.5 / 4.8 Security update
Patch Tuesday

KB5126046

KB5126046: Cumulative update for .NET Framework, versions 3.5 and 4.8, on Windows 10 21H2/22H2, September 2026. Privilege and remote-code-execution flaws addressed

In short

Two .NET Framework flaws could allow higher privileges or remote code execution. The update addresses both; restart if affected files are in use.

Does it affect you? Applies to: Devices running Windows 10 version 21H2 or 22H2 with .NET Framework 3.5 or 4.8 installed.

File version
2.0.50727.9183 · 4.8.4806.0
Security
2 fixed
Restart
Required

What changes

Fixes 2 changes

.NET Framework

2 items
  • A flaw that could let someone gain higher privileges is addressed.1
    Addresses CVE-2026-62886, a .NET Framework elevation of privilege vulnerability.
  • A flaw that could let someone run code remotely is addressed.2
    Addresses CVE-2026-69522, a .NET Framework remote code execution vulnerability.

Technical details

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

Data sheet

Released
2026-09-08
Classification
Security Updates
Type
Cumulative update
Restart
Required
Replaces
KB5120701, KB5101006
Replaced by
KB5127683
VersionFile versionChannel
3.5 2.0.50727.9183 General availability
4.8 4.8.4806.0 General availability

Security

2 vulnerabilities fixed
2 important
VulnerabilitySeverityCVSS
CVE-2026-69522
.NET and Visual Studio Remote Code Execution Vulnerability
 Important 8.8
CVE-2026-62886
.NET Elevation of Privilege Vulnerability
 Important 7.8

Downloads (Microsoft Update Catalog)

x64 Windows 10 Enterprise LTSC 2021 / Windows 10, version 22H2
78.1 MB
windows10.0-kb5126046-x64-ndp48.msu Main update · KB5126046 SHA-1: 28db9902…b8578d
Arm64 Windows 10 Enterprise LTSC 2021 / Windows 10, version 22H2
49.5 MB
windows10.0-kb5126046-arm64-ndp48.msu Main update · KB5126046 SHA-1: fce1279c…d64080
x86 Windows 10 Enterprise LTSC 2021 / Windows 10, version 22H2
49.5 MB
windows10.0-kb5126046-x86-ndp48.msu Main update · KB5126046 SHA-1: c24decf6…8d518a

Updated components

54 files changed since the previous update for the same versions.

Top changed componentsFiles
WPF33

Sources

Updated
Cited passages from Microsoft's official notes (2)
  1. 1. This security update addresses an elevation of privilege vulnerability detailed in CVE-2026-62886. support.microsoft.com
  2. 2. This security update addresses a remote code execution vulnerability detailed in CVE-2026-69522. support.microsoft.com
Checked automatically: 8 of 8 checks passed, 2 quoted passages · compared with Microsoft's page on Nov 8, 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 5/5, 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