The Update BureauKB5064399: Cumulative update for .NET Framework, versions 3.5 and 4.8, on Windows 10 21H2/22H2, September 2025. ASP.NET event logging issue addressed; WPF certificate change
Some ASP.NET error events that failed to log properly in Windows Event log are addressed. The update also includes a WPF change related to the GB18030 certificate for Chinese-language changes.
Does it affect you? Applies to: Devices running Windows 10 version 21H2 or 22H2 with .NET Framework 3.5 or 4.8 installed.
What changes
Fix 1 change
ASP.NET
For: ASP.NET applications
- Some ASP.NET error events that failed to log properly in Windows Event log are addressed.1
Improvement 1 change
WPF
For: WPF applications
-
WPF receives a change related to the GB18030 certificate for Chinese-language changes.2
WPF means Windows Presentation Foundation.
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
- KB5056577
- Replaced by
- KB5066135
| Version | File version | Channel |
|---|---|---|
| 3.5 | 2.0.50727.9179 | General availability |
| 4.8 | 4.8.4796.0 | 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 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