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

KB5066134

KB5066134: Cumulative update for .NET Framework, versions 3.5 and 4.8.1, on Windows Server 2022, October 2025. Information disclosure vulnerability addressed

In short

The update addresses CVE-2025-55248, an information disclosure vulnerability in .NET Framework 3.5 and 4.8.1 on Windows Server 2022.

Does it affect you? Applies to: Windows Server 2022 devices 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

For: Windows Server 2022 devices with .NET Framework 3.5 or 4.8.1 installed

  • An information disclosure vulnerability is addressed.1
    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
KB5065753, KB5049625
Replaced by
KB5082425
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 Server 2022
72.4 MB
windows10.0-kb5066134-x64-ndp481.msu Main update · KB5066134 SHA-1: 103b0d4c…ce0ed3

Updated components

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

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 4/5, 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