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.NET Framework 3.5

.NET Framework 3.5

Every published release for .NET Framework 3.5, newest first: what each update changes, whether to install it and any confirmed known issues.

Latest
KB5127694 Oct 13, 2026
File version
2.0.50727.9188
Released
Nov 19, 2007
All editions
updates until Jan 9, 2029
Known issues
1 open

Update history

  • .NET Framework 3.5 / 4.8.1 .NET Framework 3.5 / 4.8.1 for Windows 10 22H2 Optional preview
    Preview

    KB5039865

    WinForms memory leaks and Azure AD certificate use addressed

    Addresses memory leaks involving Windows Forms accessibility objects and an issue using x509 certificates under PPL in Azure AD. It contains no new security improvements.

    Key changes 2 changes

    • Fix Winforms: Addresses an issue involving the size of memory leaks from accessibility objects held in memory.
    • Fix .NET Fundamentals: Addresses an issue with using x509 certificates under PPL in Azure AD.
    Builds
    4.8.9251.0 · 2.0.50727.9176
    Restart
    Required
  • .NET Framework 3.5 / 4.8 .NET Framework 3.5 / 4.8 for Windows 10 22H2 Optional preview
    Preview

    KB5039867

    Windows Forms memory-leak issue addressed

    Addresses a Windows Forms memory-leak issue involving accessibility objects held in memory.

    Key changes 1 change

    • Fix Winforms: Windows Forms addresses a memory-leak issue involving accessibility objects held in memory.
    Builds
    4.8.4734.0 · 2.0.50727.9176
    Restart
    Required
  • .NET Framework 3.5 / 4.8 .NET Framework 3.5 / 4.8 for Windows 10 22H2 Optional preview
    Preview

    KB5040370

    Quality and reliability updates for .NET

    Includes cumulative .NET Framework updates for Windows 10 version 22H2. The page points to separate articles for the quality and reliability details.

    Check the newer update, KB5041355

    Key changes 2 changes

    • Improved .NET Framework 3.5 and 4.8: This update includes quality and reliability improvements for .NET Framework 3.5 and 4.8; the page links to an article with details.
    • Improved .NET Framework 3.5 and 4.8.1: This update includes quality and reliability improvements for .NET Framework 3.5 and 4.8.1; the page links to an article with details.
    Restart
    Required
  • .NET Framework 3.5 / 4.8.1 .NET Framework 3.5 / 4.8.1 for Windows 10 21H2, 22H2 Optional preview
    Preview

    KB5037587

    WPF crashes and CLR query errors addressed

    Addresses reliability issues in .NET Framework, including app crashes in WPF and the CLR. It adds no new security improvements.

    Check the newer update, KB5039893

    Key changes 6 changes

    • Fix CLR: Addresses a problem that can cause crashes when several threads query the same managed type.
    • Fix CLR: Addresses cases where symbol-reading APIs might return incorrect results.
    • Fix .NET Libraries: Addresses an issue that can be triggered in the FBX file parser.
    Builds
    4.8.9241.0 · 2.0.50727.9176
    Restart
    Required
  • .NET Framework 3.5 / 4.8.1 .NET Framework 3.5 / 4.8.1 for Windows Server 2022 Update

    KB5037929

    WPF window-text crashes and .NET runtime errors addressed

    Apps that read window text can crash, and some SQL CLR apps can hit runtime errors with specific hash types. This update also addresses issues in IIS 10 and .NET libraries.

    Check the newer update, KB5039907

    Key changes 6 changes

    • Fix CLR: Crashes from simultaneous queries of the same managed type are addressed.
    • Fix CLR: Two APIs that find methods by document position can return incorrect results in some cases; this issue is addressed.
    • Fix .NET Libraries: An issue in the FBX file parser is addressed.
    Builds
    4.8.9246.0 · 2.0.50727.9176
    Restart
    Required
  • .NET Framework 3.5 / 4.8 .NET Framework 3.5 / 4.8 for Windows 10 21H2, 22H2 Optional preview
    Preview

    KB5037592

    WPF app crashes and 32-bit response delays addressed

    Addresses several .NET reliability problems, including some app crashes and slow responses on 32-bit platforms. A restart might be needed if affected files are in use.

    Check the newer update, KB5039884

    Key changes 5 changes

    • Fix CLR: Some apps can crash when multiple background tasks check the same kind of information at the same time.
    • Fix .NET Libraries: The update addresses unusually slow response times on 32-bit platforms.
    • Fix .NET Libraries: The update addresses how .NET chooses validated methods for security-related calculations.
    Builds
    4.8.4724.0 · 2.0.50727.9176
    Restart
    Required
  • .NET Framework 3.5 / 4.8 .NET Framework 3.5 / 4.8 for Windows Server 2022 Update

    KB5037930

    WPF app crashes and concurrent type-query failures addressed

    Concurrent type queries can crash the .NET runtime, and WPF apps can crash when reading window text. A later update, KB5043743, resolves a separate SQL CLR runtime exception.

    Check the newer update, KB5039889

    Key changes 5 changes

    • Fix CLR: Concurrent checks of the same managed type can crash the runtime; this update addresses the problem.
    • Fix .NET Libraries: Some 32-bit platforms can have much slower response times; this update addresses the slowdown.
    • Fix .NET Libraries: The update addresses an issue with using MIST-validated FIPS algorithms.
    Builds
    4.8.4729.0 · 2.0.50727.9176
    Restart
    Required
  • .NET Framework 3.5 / 4.8 .NET Framework 3.5 / 4.8 for Windows 10 1809 · Windows Server 2019 Update

    KB5037933

    Three SQL CLR hash constructors trigger errors; later fixed

    Runtime exceptions can occur in SQL CLR code that creates SHA256Managed, SHA384Managed, or SHA512Managed objects; KB5043804 resolves the issue. The update also addresses .NET reliability problems.

    Check the newer update, KB5039886

    Key changes 5 changes

    • Fix CLR: Crashes can occur when several threads query the same managed type at once. The update addresses this issue.
    • Fix .NET Libraries: Some 32-bit devices can have much slower response times. The update addresses this issue.
    • Fix .NET Libraries: The update addresses an issue with validated FIPS algorithm implementations.
    Builds
    4.8.4729.0 · 2.0.50727.9063
    Restart
    Required
  • .NET Framework 3.5 / 4.7.2 .NET Framework 3.5 / 4.7.2 for Windows 10 1809 · Windows Server 2019 Update

    KB5037932

    Concurrent .NET crashes and 32-bit response delays addressed

    The update addresses possible .NET runtime crashes during concurrent type queries and a response-time regression on 32-bit platforms. You must restart the computer after applying it if any affected files are in use.

    Check the newer update, KB5039879

    Key changes 2 changes

    • Fix CLR: Addresses crashes that can occur when several threads query the same managed type at the same time.
    • Fix .NET Libraries: Addresses a significant response-time slowdown on 32-bit platforms.
    Builds
    4.7.4095.0 · 2.0.50727.9063
    Restart
    Required
  • .NET Framework 3.5 / 4.8 .NET Framework 3.5 / 4.8 for Windows 10 22H2 Optional preview
    Preview

    KB5037724

    Earlier security protections remain included

    This .NET Framework preview keeps earlier security protections and includes quality and reliability improvements. Windows Update installs it automatically on Windows 10 version 22H2.

    Check the newer update, KB5040370

    Key changes 2 changes

    • Improved Security: Earlier security protections remain part of this cumulative update.
    • Improved .NET Framework: The update includes quality and reliability improvements. The page links to articles with details.
    Restart
    Required
  • .NET Framework 3.5 / 4.8.1 .NET Framework 3.5 / 4.8.1 for Windows 10 21H2, 22H2 Security update

    KB5036618

    Remote code execution flaw addressed; .NET reliability issues improved

    Addresses CVE-2024-21409, a .NET Framework remote code execution vulnerability, and several reliability and performance issues in ASP.NET, the CLR, and the C# compiler.

    Check the newer update, KB5039893

    Key changes 1 CVE · 7 changes

    • Fix .NET Framework: Addresses a remote code execution vulnerability in .NET Framework.
    • Fix .NET Framework: Addresses an issue caused by an outdated version of the OSS zlib library.
    • Fix .NET Framework: Addresses an issue in the AIA fetching process.
    Security
    1 vulnerability fixed
    Restart
    Required
  • .NET Framework 3.5 / 4.8.1 .NET Framework 3.5 / 4.8.1 for Windows Server 2022 Security update

    KB5036621

    Remote code execution flaw and application slowdowns addressed

    The update addresses CVE-2024-21409, a .NET Framework flaw that could let an attacker run code, and addresses several reliability and performance problems.

    Check the newer update, KB5039907

    Key changes 1 CVE · 7 changes

    • Fix .NET Framework: A security flaw that could let an attacker run code is addressed.
    • Fix .NET Framework: A security issue involving an outdated library used by .NET is addressed.
    • Fix .NET Framework: A security issue in a .NET data-fetching process is addressed.
    Builds
    4.8.9236.0 · 2.0.50727.9176
    Security
    1 vulnerability fixed
    Restart
    Required
  • .NET Framework 3.5 / 4.8 .NET Framework 3.5 / 4.8 for Windows 10 21H2, 22H2 Security update

    KB5036608

    Patches a remote code flaw and addresses unresponsive task queues

    The update addresses a remote code-execution flaw in .NET and two other security issues. It also tackles slowdowns in ASP.NET apps and background tasks that stop responding.

    Check the newer update, KB5039884

    Key changes 1 CVE · 5 changes

    • Fix .NET Framework: A security flaw that could let an attacker run code on a device remotely is addressed.
    • Fix .NET Framework: A security issue involving an outdated component used by .NET is addressed.
    • Fix .NET Framework: A security issue in a .NET process that fetches information is addressed.
    Builds
    4.8.4718.0 · 2.0.50727.9176
    Security
    1 vulnerability fixed
    Restart
    Required
  • .NET Framework 3.5 / 4.8 .NET Framework 3.5 / 4.8 for Windows Server 2022 Security update

    KB5036613

    Remote-code flaw addressed; serializer slowdown improved

    The update addresses CVE-2024-21409, a .NET Framework remote code execution flaw, and reliability problems in ASP.NET and the CLR.

    Check the newer update, KB5039889

    Key changes 1 CVE · 5 changes

    • Fix .NET Framework: Addresses a remote code execution vulnerability in .NET Framework.
    • Fix .NET Framework: Addresses a security issue involving an outdated OSS zlib library.
    • Fix .NET Framework: Addresses a security issue in the AIA fetching process.
    Builds
    4.8.4718.0 · 2.0.50727.9176
    Security
    1 vulnerability fixed
    Restart
    Required
  • .NET Framework 3.5 / 4.8 .NET Framework 3.5 / 4.8 for Windows 10 1809 · Windows Server 2019 Security update

    KB5036610

    Remote code execution flaw addressed; ASP.NET slowdown tackled

    Addresses a .NET Framework remote code execution vulnerability and reliability issues, including an ASP.NET performance drop after the January update.

    Check the newer update, KB5039886

    Key changes 1 CVE · 5 changes

    • Fix .NET Framework: A remote code execution vulnerability in .NET Framework is addressed.
    • Fix .NET Framework: An outdated software library version is addressed.
    • Fix .NET Framework: A problem with an information-fetching process is addressed.
    Builds
    4.8.4718.0 · 2.0.50727.9063
    Security
    1 vulnerability fixed
    Restart
    Required
  • .NET Framework 3.5 / 4.7.2 .NET Framework 3.5 / 4.7.2 for Windows 10 1809 · Windows Server 2019 Security update

    KB5036604

    ASP.NET slowdown fixed; security flaws addressed

    The update addresses a security flaw that could let an attacker run code on an affected system, updates an outdated library, and addresses an ASP.NET performance slowdown.

    Check the newer update, KB5039879

    Key changes 1 CVE · 4 changes

    • Fix .NET Framework: Addresses a security flaw that could let an attacker run code on an affected system.
    • Fix .NET Framework: Updates an outdated library version as part of a security improvement.
    • Fix .NET Framework: Addresses a security issue in a data-fetching process.
    Builds
    4.7.4092.0 · 2.0.50727.9063
    Security
    1 vulnerability fixed
    Restart
    Required
  • .NET Framework 3.5 / 4.8.1 .NET Framework 3.5 / 4.8.1 for Windows 10 22H2 Optional preview
    Preview

    KB5036034

    ASP.NET performance and .NET runtime issues addressed

    Addresses a performance issue in ASP.NET and several .NET runtime and compiler issues. A restart is required if affected files are in use.

    Key changes 4 changes

    • Fix .NET Libraries: Addresses a performance issue in ASP.NET applications after installing the January 2024 .NET Framework update.
    • Fix .NET Runtime: Addresses an issue that can make thread pool recycled lists unresponsive on computers with multiple CPU groups.
    • Fix .NET Runtime: Addresses an issue where Interlocked.Read from 32-bit apps runs much slower on some computers.
    Builds
    4.8.9232.0 · 2.0.50727.9176
    Restart
    Required
  • .NET Framework 3.5 / 4.8 .NET Framework 3.5 / 4.8 for Windows 10 22H2 Optional preview
    Preview

    KB5036036

    ASP.NET performance and thread-pool stalls addressed

    Addresses an ASP.NET performance issue after the January 2024 .NET Framework update and an issue that could make thread-pool lists unresponsive on computers with multiple CPU groups.

    Key changes 2 changes

    • Fix .NET Libraries: Addresses an ASP.NET performance issue that occurred after installing the January 2024 .NET Framework update.
    • Fix .NET Runtime: Addresses an issue that could make thread-pool lists unresponsive on computers with multiple CPU groups.
    Builds
    4.8.4712.0 · 2.0.50727.9176
    Restart
    Required
  • .NET Framework 3.5 / 4.8 .NET Framework 3.5 / 4.8 for Windows 10 22H2 Optional preview
    Preview

    KB5036580

    .NET 3.5, 4.8 and 4.8.1 get quality changes

    Includes cumulative quality and reliability improvements for .NET Framework 3.5, 4.8 and 4.8.1 on Windows 10, version 22H2. Windows Update downloads and installs it automatically.

    Check the newer update, KB5037724

    Key changes 1 change

    • Improved .NET Framework: Quality and reliability improvements are included for .NET Framework 3.5, 4.8 and 4.8.1.
    Restart
    Required
  • .NET Framework 3.5 / 4.8.1 .NET Framework 3.5 / 4.8.1 for Windows 10 21H2, 22H2 Optional preview
    Preview

    KB5034466

    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.

    Check the newer update, KB5036618

    Key changes 2 changes

    • Fix ASP.NET: An issue with an “Illegal characters in path” error in some ASP.NET MVC requests is addressed.
    • Fix .NET Libraries: An issue with an out-of-date zlib library version in .NET is addressed.
    Builds
    4.8.9220.0 · 2.0.50727.9176
    Restart
    Required
  • .NET Framework 3.5 / 4.8.1 .NET Framework 3.5 / 4.8.1 for Windows Server 2022 Update

    KB5034611

    ASP.NET path errors addressed; outdated zlib library

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

    Check the newer update, KB5036621

    Key changes 2 changes

    • Fix ASP.NET: The update addresses an “Illegal characters in path” error in some ASP.NET MVC requests.
    • Fix .NET Libraries: The update addresses an issue with an outdated zlib library.
    Builds
    4.8.9224.0 · 2.0.50727.9176
    Restart
    Required
  • .NET Framework 3.5 / 4.8 .NET Framework 3.5 / 4.8 for Windows 10 21H2, 22H2 Optional preview
    Preview

    KB5034468

    ASP.NET MVC path errors and outdated zlib version addressed

    The update addresses an error in some ASP.NET MVC requests and an issue with an outdated zlib library. If you already installed it in the January 23 rollup, no action is needed.

    Check the newer update, KB5036608

    Key changes 2 changes

    • Fix ASP.NET: The update addresses an error that can occur in some ASP.NET MVC requests with illegal characters in the path.
    • Fix .NET Libraries: The update addresses an issue with an outdated version of the open-source zlib library.
    Builds
    4.8.4697.0 · 2.0.50727.9176
    Restart
    Required
  • .NET Framework 3.5 / 4.8 .NET Framework 3.5 / 4.8 for Windows Server 2022 Update

    KB5034613

    ASP.NET MVC path errors and an outdated zlib library addressed

    The update addresses an “Illegal characters in path” error in some ASP.NET MVC requests and an outdated version of the OSS zlib library.

    Check the newer update, KB5036613

    Key changes 2 changes

    • Fix ASP.NET: The update addresses an “Illegal characters in path” error in some ASP.NET MVC requests.
    • Fix .NET Libraries: The update addresses an outdated version of the OSS zlib library.
    Builds
    4.8.4700.0 · 2.0.50727.9176
    Restart
    Required
  • .NET Framework 3.5 / 4.8 .NET Framework 3.5 / 4.8 for Windows 10 1809 · Windows Server 2019 Update

    KB5034624

    ASP.NET MVC path errors and outdated zlib addressed

    Addresses an illegal-path error in some ASP.NET MVC requests and an outdated OSS zlib library version. It contains no new security improvements.

    Check the newer update, KB5036610

    Key changes 2 changes

    • Fix ASP.NET: Some ASP.NET MVC requests no longer encounter an illegal-characters-in-path error.
    • Fix .NET Libraries: Addresses an issue with the outdated version of the OSS zlib library.
    Builds
    4.8.4700.0 · 2.0.50727.9063
    Restart
    Required
  • .NET Framework 3.5 / 4.7.2 .NET Framework 3.5 / 4.7.2 for Windows 10 1809 · Windows Server 2019 Update

    KB5034619

    Illegal-path errors in some ASP.NET MVC requests addressed

    The update addresses an illegal-path error in some ASP.NET MVC requests. It adds no new security improvements but includes previously released ones.

    Check the newer update, KB5036604

    Key changes 1 change

    • Fix ASP.NET: The update addresses an illegal-path error in some ASP.NET MVC requests.
    Builds
    4.7.4087.0 · 2.0.50727.9063
    Restart
    Required