The Update BureauKB5064400: Cumulative update for .NET Framework, versions 3.5 and 4.8.1, on Windows 10 21H2/22H2, September 2025. ASP.NET event logging fixed; GB18030 certificate updated
The update addresses ASP.NET event logging and a GB18030 certificate update for Chinese-language changes. If you already installed the August 26 release, you do not need to take action.
Does it affect you? Applies to: Devices running Windows 10, version 21H2 or 22H2, with .NET Framework 3.5 or 4.8.1 installed.
What changes
Fix 1 change
ASP.NET
-
Some ASP.NET error events that failed to appear in the Windows Event log are addressed.1
Addresses an issue where some error events fail to log properly in the Windows Event log.
Improvement 1 change
WPF
For: Devices using WPF
- The GB18030 certificate receives an update related to Chinese-language changes.2
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
- KB5056578
- Replaced by
- KB5066130
| Version | File version | Channel |
|---|---|---|
| 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.
Downloads (Microsoft Update Catalog)
Updated components
75 files changed since the previous update for the same versions.
| Top changed components | Files |
|---|---|
| WPF | 33 |
| ASP.NET | 15 |
Verified in package: changed files confirm ASP.NET, WPF.
Sources
Cited passages from Microsoft's official notes (2)
-
1.
Addressed an issue in ASP.NET where some error events fail to log properly in the Windows Event log.
support.microsoft.com -
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 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