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.NET Framework 3.5 / 4.8.1 .NET Framework 3.5 / 4.8.1 Optional preview
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KB5064403

KB5064403: Cumulative update for .NET Framework, versions 3.5 and 4.8.1, on Windows 11 23H2, September 2025. ASP.NET event logging and GB18030 certificate handling updated

In short

The update addresses ASP.NET error events that might not be logged properly and a WPF update for the GB18030 certificate used in Chinese language changes.

Does it affect you? Applies to: Devices running Windows 11, version 22H2 or 23H2, with .NET Framework 3.5 or 4.8.1 installed.

File version
2.0.50727.9179 · 4.8.9316.0
Restart
Required
Review notes Additional details from the official release notes (1) Read note
  • What changes The update addresses a problem where some ASP.NET error events failed to log properly in the Windows Event log.

The official sources are linked at the end of the page.

What changes

Fix 1 change

ASP.NET

Verified in package
  • Some ASP.NET error events are logged properly in the Windows Event log.1
    Addresses an issue where some error events fail to log properly in the Windows Event log.

Improvement 1 change

WPF

Verified in package
  • Includes an update for the GB18030 certificate for Chinese language changes.2
    Windows Presentation Foundation (WPF) receives an update for the GB18030 certificate for Chinese language changes.

Technical details

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

Data sheet

Released
2025-09-09
Classification
Updates
Type
Cumulative update
Restart
Required
Replaces
KB5056580
Replaced by
KB5066133
VersionFile versionChannel
3.5 2.0.50727.9179 General availability
4.8.1 4.8.9316.0 General availability

Security

No vulnerabilities are listed for this update.

Updated components

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

Top changed componentsFiles
WPF22
ASP.NET10

Verified in package: changed files confirm ASP.NET, WPF.

Sources

Updated
Cited passages from Microsoft's official notes (2)
  1. 1. Addressed an issue in ASP.NET where some error events fail to log properly in the Windows Event log. support.microsoft.com
  2. 2. Addressed an update for GB18030 certificate for Chinese language changes. support.microsoft.com
Checked automatically: 8 of 8 checks passed, 2 quoted passages · 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: passed

A second AI read the text against the sources: correctness 3/5, 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