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.NET Framework 3.5 / 4.8.1 .NET Framework 3.5 / 4.8.1 Security update
Patch Tuesday

KB5049624

KB5049624: Cumulative update for .NET Framework, versions 3.5 and 4.8.1, on Windows 11 23H2, January 2025. .NET RCE flaw addressed; rare CLR loop fixed

In short

The update addresses a .NET Framework remote code execution vulnerability and a rare infinite-loop issue when a thread first enters the CLR. It is no longer available through Windows Update.

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 · 4.8.9290.0
Security
1 fixed
Restart
Required

What changes

Fixes 2 changes

.NET Framework

For: Devices with .NET Framework 3.5 or 4.8.1 installed

  • A remote code execution vulnerability in .NET Framework is addressed.1
    Addresses CVE-2025-21176.

.NET Runtime

For: Devices running .NET Framework applications

  • A rare issue that could cause an infinite loop when a thread first enters the CLR is addressed.2

Technical details

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

Data sheet

Released
2025-01-14
Classification
Security Updates
Type
Cumulative update
Restart
Required
Replaced by
KB5066133
VersionFile versionChannel
3.5 2.0.50727.9179 General availability
4.8.1 4.8.9290.0 General availability

Security

1 vulnerability fixed
1 important
VulnerabilitySeverityCVSS
CVE-2025-21176
.NET, .NET Framework, and Visual Studio Remote Code Execution Vulnerability
 Important 8.8

Sources

Updated
Cited passages from Microsoft's official notes (2)
  1. 1. This security update addresses a remote code execution vulnerability detailed in CVE-2025-21176. support.microsoft.com
  2. 2. Addresses an issue where in rare cases where an infinite loop could occur when a thread enters CLR for the first time. 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