The Update BureauKB5034466: Cumulative update for .NET Framework, versions 3.5 and 4.8.1, on Windows 10 21H2/22H2, February 2024. ASP.NET path errors and an outdated zlib version addressed
The update addresses an illegal-path error in some ASP.NET MVC requests and an outdated OSS zlib library version in .NET.
Does it affect you? Applies to: Windows 10, versions 21H2 and 22H2, and Windows 10 Enterprise LTSC 2021 devices with .NET Framework 3.5 or 4.8.1 installed.
What changes
Fixes 2 changes
ASP.NET
For: ASP.NET application developers
-
An issue with an “Illegal characters in path” error in some ASP.NET MVC requests is addressed.1
The error is
System.ArgumentException: Illegal characters in path.
.NET Libraries
For: .NET application developers
-
An issue with an out-of-date zlib library version in .NET is addressed.2
The affected library is OSS zlib.
Technical details
Data sheet · Security · Downloads · Components Click to collapse or expand
Data sheet
- Released
- 2024-02-13
- Classification
- Updates
- Type
- Cumulative update
- Restart
- Required
- Replaced by
- KB5036618
| Version | File version | Channel |
|---|---|---|
| 3.5 | 2.0.50727.9176 | General availability |
| 4.8.1 | 4.8.9220.0 | General availability |
Security
No vulnerabilities are listed for this update.
Downloads (Microsoft Update Catalog)
Updated components
78 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.
Sources
Cited passages from Microsoft's official notes (2)
-
1.
Addresses an issue with "System.ArgumentException: Illegal characters in path" in some ASP.Net MVC requests.
support.microsoft.com -
2.
Addresses an issue where version of the OSS zlib library is out of date.
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 4/5. 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