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.NET Framework 3.5 / 4.8.1 .NET Framework 3.5 / 4.8.1 Security update
Patch Tuesday

KB5066130

KB5066130: Cumulative update for .NET Framework, versions 3.5 and 4.8.1, on Windows 10 21H2/22H2, October 2025. Information disclosure flaw in the application runtime addressed

In short

The update addresses CVE-2025-55248, an information disclosure vulnerability in .NET Framework. Restart your computer 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 4.8.1 installed.

File version
2.0.50727.9180 · 4.8.9320.0
Security
1 fixed
Restart
Required

What changes

Fix 1 change

.NET Framework

  • An information disclosure vulnerability in .NET Framework is addressed.1
    Addresses CVE-2025-55248.

Technical details

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

Data sheet

Released
2025-10-14
Classification
Security Updates
Type
Cumulative update
Restart
Required
Replaces
KB5064400, KB5049621
Replaced by
KB5082419
VersionFile versionChannel
3.5 2.0.50727.9180 General availability
4.8.1 4.8.9320.0 General availability

Security

1 vulnerability fixed
1 not rated
VulnerabilitySeverityCVSS
CVE-2025-55248
.NET, .NET Framework, and Visual Studio Information Disclosure Vulnerability
 Not rated —

Downloads (Microsoft Update Catalog)

x64 Windows 10 Enterprise LTSC 2021 / Windows 10, version 22H2
75.7 MB
windows10.0-kb5066130-x64-ndp481.msu Main update · KB5066130 SHA-1: 62d1e2cb…986fa6
x86 Windows 10 Enterprise LTSC 2021 / Windows 10, version 22H2
47.1 MB
windows10.0-kb5066130-x86-ndp481.msu Main update · KB5066130 SHA-1: d1252c77…69d6ab

Updated components

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

Top changed componentsFiles
WPF36
.NET runtime (CLR)18
ASP.NET15

Sources

Updated
Cited passages from Microsoft's official notes (1)
  1. 1. This security update addresses an information disclosure vulnerability detailed in CVE-2025-55248. support.microsoft.com
Checked automatically: 7 of 8 checks passed, 1 quoted passage · compared with Microsoft's page on Oct 20, 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: not 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