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.NET Framework 3.5 / 4.8.1 .NET Framework 3.5 / 4.8.1 Update
Patch Tuesday

KB5034611

KB5034611: Cumulative update for .NET Framework, versions 3.5 and 4.8.1, on Windows Server 2022, February 2024. ASP.NET path errors addressed; outdated zlib library

In short

Addresses an “Illegal characters in path” error in some ASP.NET MVC requests and an issue with an outdated zlib library.

Does it affect you? Applies to: Windows Server 2022 devices with .NET Framework 3.5 or 4.8.1 installed.

File version
2.0.50727.9176 · 4.8.9224.0
Restart
Required

What changes

Fixes 2 changes

ASP.NET

Verified in package

For: Servers handling some ASP.NET MVC requests

  • The update addresses an “Illegal characters in path” error in some ASP.NET MVC requests.1
    Addresses an issue with System.ArgumentException: Illegal characters in path in some ASP.NET MVC requests.

.NET Libraries

For: Windows Server 2022 devices with .NET Framework installed

  • The update addresses an issue with an outdated zlib library.2
    Addresses an issue where the version of the OSS zlib library is out of date.

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
KB5036621
VersionFile versionChannel
3.5 2.0.50727.9176 General availability
4.8.1 4.8.9224.0 General availability

Security

No vulnerabilities are listed for this update.

Downloads (Microsoft Update Catalog)

x64 Windows Server 2022
61.3 MB
windows10.0-kb5034611-x64-ndp481.msu Main update · KB5034611 SHA-1: 761e979f…f98421

Updated components

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

Top changed componentsFiles
WPF22
ASP.NET10

Verified in package: changed files confirm ASP.NET.

Sources

Updated
Cited passages from Microsoft's official notes (2)
  1. 1. Addresses an issue with "System.ArgumentException: Illegal characters in path" in some ASP.Net MVC requests. support.microsoft.com
  2. 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 Addresses an issue where version of the OSS zlib library is out of date.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 4/5, 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