.NET Framework October 2020 Security and Quality Rollup Updates

Tara Overfield


Today, we are releasing the October 2020 Security and Quality Rollup Updates for .NET Framework.


CVE-2020-16937– .NET Framework Information Disclosure Vulnerability

An information disclosure vulnerability exists when the .NET Framework improperly handles objects in memory. An attacker who successfully exploited the vulnerability could disclose contents of an affected system’s memory. To exploit the vulnerability, an authenticated attacker would need to run a specially crafted application. The update addresses the vulnerability by correcting how the .NET Framework handles objects in memory.

To learn more about the vulnerabilities, go to the following Common Vulnerabilities and Exposures (CVE).

Quality and Reliability

This release contains the following quality and reliability improvements.

  • Disabled resuse of AppPathModifier in ASP.Net control output.
  • HttpCookie objects in the ASP.Net request context will be created with configured defaults for cookie flags instead of .NET-style primitive defaults to match the behavior of `new HttpCookie(name)`.
  • Added a CLR config variable Thread_AssignCpuGroups (1 by default) that can be set to 0 to disable automatic CPU group assignment done by the CLR for new threads created by Thread.Start() and thread pool threads, such that an app may do its own thread-spreading.
  • Addressed a rare data corruption that can occur when using new API’s such as Unsafe.ByteOffset which are often used with the new Span types. The corruption could occur when a GC operation is performed while a thread is calling Unsafe.ByteOffset from inside of a loop.
  • Addressed a failure that sometimes occured when a user connects to one Azure SQL database, performed an enclave based operation, and then connected to another database under the same server that has the same Attestation URL and performed an enclave operation on the second server.
Windows Forms
  • Addressed a regression introduced in .NET Framework 4.8, where Control.AccessibleName, Control.AccessibleRole, and Control.AccessibleDescription properties stopped working for the following controls:Label, GroupBox, ToolStrip, ToolStripItems, StatusStrip, StatusStripItems, PropertyGrid, ProgressBar, ComboBox, MenuStrip, MenuItems, DataGridView.
  • Addressed a regression in accessible name for combo box items for data bound combo boxes. .NET Framework 4.8 started using type name instead of the value of the DisplayMember property as an accessible name, this improvement uses the DisplayMember again.
  • Addressed an issue with WCF services sometimes failing to start when starting multiple services concurrently.

1 Common Language Runtime (CLR) 2 Windows Communication Foundation (WCF)

Getting the Update

The Security and Quality Rollup is available via Windows Update, Windows Server Update Services, and Microsoft Update Catalog. The Security Only Update is available via Windows Server Update Services and Microsoft Update Catalog.

Microsoft Update Catalog

You can get the update via the Microsoft Update Catalog. For Windows 10, NET Framework 4.8 updates are available via Windows Update, Windows Server Update Services, Microsoft Update Catalog. Updates for other versions of .NET Framework are part of the Windows 10 Monthly Cumulative Update.

**Note**: Customers that rely on Windows Update and Windows Server Update Services will automatically receive the .NET Framework version-specific updates. Advanced system administrators can also take use of the below direct Microsoft Update Catalog download links to .NET Framework-specific updates. Before applying these updates, please ensure that you carefully review the .NET Framework version applicability, to ensure that you only install updates on systems where they apply.

The following table is for Windows 10 and Windows Server 2016+ versions.

Product VersionCumulative Update
Windows 10 Version Next and Windows Server, Version Next
.NET Framework 3.5, 4.8Catalog4578967
Windows 10, version 20H2 and Windows Server, version 20H2
.NET Framework 3.5, 4.8Catalog4578968
Windows 10 2004 and Windows Server, version 2004
.NET Framework 3.5, 4.8Catalog4578968
Windows 10 1909 and Windows Server, version 1909
.NET Framework 3.5, 4.8Catalog4578974
Windows 10 1903 and Windows Server, version 1903
.NET Framework 3.5, 4.8Catalog4578974
Windows 10 1809 (October 2018 Update) and Windows Server 20194579976
.NET Framework 3.5, 4.7.2Catalog4578966
.NET Framework 3.5, 4.8Catalog4578973
Windows 10 1803 (April 2018 Update)
.NET Framework 3.5, 4.7.2Catalog4580330
.NET Framework 4.8Catalog4578972
Windows 10 1709 (Fall Creators Update)
.NET Framework 3.5, 4.7.1, 4.7.2Catalog4580328
.NET Framework 4.8Catalog4578971
Windows 10 1703 (Creators Update)
.NET Framework 3.5, 4.7, 4.7.1, 4.7.2Catalog4580370
.NET Framework 4.8Catalog4578970
Windows 10 1607 (Anniversary Update) and Windows Server 2016
.NET Framework 3.5, 4.6.2, 4.7, 4.7.1, 4.7.2Catalog4580346
.NET Framework 4.8Catalog4578969
Windows 10 1507
.NET Framework 3.5, 4.6, 4.6.1, 4.6.2Catalog4580327

The following table is for earlier Windows and Windows Server versions.

Product VersionSecurity and Quality RollupSecurity Only Update
Windows 8.1, Windows RT 8.1 and Windows Server 2012 R245799794580469
.NET Framework 3.5Catalog4578953Catalog4578981
.NET Framework 4.5.2Catalog4578956Catalog4578984
.NET Framework 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2Catalog4578962Catalog4578986
.NET Framework 4.8Catalog4578976Catalog4578989
Windows Server 201245799784580468
.NET Framework 3.5Catalog4578950Catalog4578978
.NET Framework 4.5.2Catalog4578954Catalog4578982
.NET Framework 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2Catalog4578961Catalog4578985
.NET Framework 4.8Catalog4578975Catalog4578988
Windows 7 SP1 and Windows Server 2008 R2 SP145799774580467
.NET Framework 3.5.1Catalog4578952Catalog4578980
.NET Framework 4.5.2Catalog4578955Catalog4578983
.NET Framework 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2Catalog4578963Catalog4578987
.NET Framework 4.8Catalog4578977Catalog4578990
Windows Server 200845799804580470
.NET Framework 2.0, 3.0Catalog4578951Catalog4578979
.NET Framework 4.5.2Catalog4578955Catalog4578983
.NET Framework 4.6Catalog4578963Catalog4578987


Previous Monthly Rollups

The last few .NET Framework Monthly updates are listed below for your convenience:


Leave a comment

  • Avatar
    Ismail Demir

    About fragmented Updates

    An example to show you whats going wrong with netfx or general windows updates.

    TL;DR: The combination of both updates kb3037574 and kb2861698 supersede kb2656356

    Windows 7 SP1+ NetFramework Updates

    1) Following 3 updates are available via Windows Update

    [kb2656356] ‘dated 2011

    [kb2861698] ‘dated 2013

    [kb3037574] ‘dated 2015

    2) Supersedence

    kb2656356 vs kb2861698

    kb2861698 has updated system.web.extensions.dll version.
    And also a new file: system.servicemodel.web.dll which kb2656356 hasn’t.
    But on the other side the kb2861698 has missing some files from kb2656356 to
    supersede kb2656356.

    kb2656356 vs kb3037574

    kb3037574 has 3 new files and 4 updated files.
    Only one file (system.web.extensions.dll) is missing from kb3037574 to supersede kb2656356.

    3) Result: The combination of both
    Now the combination of the two updates, kb2861698 and kb3037574 [should be] supersede the kb2656356!
    -> All files gets replaced with a newer version.

    Its just an example of my findings…There is more!

    Note: Registry entries are not included

  • Stav Kaufman
    Stav Kaufman

    Thank you for this summary of October .NET patches.

    I’m trying to understand supersedence relations between the .NET patches of last 3 months.
    I understand there’s this relation:
    4579979 (oct)–> 4576630 (sep)–>4570508 (aug) of parents
    and this of children: (in this case .NET 3.5 on Windows 8.1 and 2012 R2)
    4578953 (oct) –> 4569768 (aug)

    But could not find anywhere how to relate the patches for 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2 on Windows 8.1 and 2012 R2.
    How can I find out if
    4578962 (oct) -?-> 4576614 (sep) -?-> 4569774 (aug)
    other than guessing…?

    Same question with regards the 4.8 updates for these Windows versions.

    Thank you very much in advance.