Security Only Update for .NET Framework 3.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8 for Windows 7 SP1 and Windows Server 2008 R2 SP1 (KB4556403)

Notice

Revised 6/8/2021 On June 8th, 2021, this update was released to replace a previous update to address a “revocation server was offline” error that may occur during installation. If you’ve already installed a previous release of this update, no action is required. To obtain the latest version of these updates, see the “How to obtain and install the update” section of the individual update article. Links to each article are found in the “Additional information about this update” section of this article. On April 13th, 2021, this update was released to replace a previous release of this update.On July 23, 2020, update KB4552952 v2, KB4552951 v2, and KB4552953 v2 were released to replace v1 of those updates for .NET Framework 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, and 4.8 for Windows 7 Service Pack 1 (SP1) and Windows Server 2008 R2 SP1. The v1 updates did not install for customers who had certain ESU configurations. The v2 updates correct the issue for customers who could not install the v1 updates.

**Applies to:**Microsoft .NET Framework 3.5.1 Microsoft .NET Framework 4.5.2 Microsoft .NET Framework 4.6 Microsoft .NET Framework 4.6.1 Microsoft .NET Framework 4.6.2 Microsoft .NET Framework 4.7 Microsoft .NET Framework 4.7.1 Microsoft .NET Framework 4.7.2 Microsoft .NET Framework 4.8

IMPORTANT Verify that you have installed the required updates listed in theHow to get this update section before installing this update.

IMPORTANTSome customers who use Windows Server 2008 R2 SP1 and have activated their ESU multiple activation key (MAK) add-on before installing the January 14, 2020 updates might need to re-activate their key. Re-activation on the affected devices should only be required once. For information on activation, see this blog post.

IMPORTANTWSUS scan cab files will continue to be available for Windows 7 SP1 and Windows Server 2008 R2 SP1. If you have a subset of devices running these operating systems without ESU, they might show as non-compliant in your patch management and compliance toolsets.

IMPORTANTCustomers who have purchased the Extended Security Update (ESU) for on-premises versions of these operating systems must follow the procedures in KB4522133 to continue receiving security updates after extended support ends on January 14, 2020. For more information on ESU and which editions are supported, see KB4497181.

IMPORTANTStarting on January 15, 2020, a full-screen notification will appear that describes the risk of continuing to use Windows 7 Service Pack 1 after it reaches end of support on January 14, 2020. The notification will remain on the screen until you interact with it. This notification will only appear on the following editions of Windows 7 Service Pack 1:NoteThe notification will not appear on domain-joined machines or machines in kiosk mode.

• Starter.
• Home Basic.
• Home Premium.
• Professional. If you have purchased the Extended Security Update (ESU), the notification will not appear. For more information, see How to get Extended Security Updates for eligible Windows devices and Lifecycle FAQ-Extended Security Updates.
• Ultimate.

IMPORTANT Starting in August, 2019, updates to .NET Framework 4.6 and above, for Windows Server 2008 R2 SP1, and Windows 7SP1, require SHA-2 Code signing support. Please make sure that you have all the latest Windows Updates before applying this update to avoid installation issues. For more detailed information about SHA-2 code signing support updates, please see KB 4474419.

IMPORTANT All updates for .NET Framework 4.7.2, 4.7.1, 4.7, 4.6.2, 4.6.1, and 4.6 require that the d3dcompiler_47.dll update is installed. We recommend that you install the included d3dcompiler_47.dll update before you apply this update. For more information about the d3dcompiler_47.dll, see KB 4019990.

IMPORTANT If you install a language pack after you install this update, you must reinstall this update. Therefore, we recommend that you install any language packs that you need before you install this update. For more information, see Add language packs to Windows.

Summary

An elevation of privilege vulnerability exists in .NET Framework which could allow an attacker to elevate their privilege level. To exploit the vulnerability, an attacker would first have to access the local machine, and then run a malicious program. The update addresses the vulnerability by correcting how .NET Framework activates COM objects.To learn more about the vulnerabilities, go to the following Common Vulnerabilities and Exposures (CVE).

• CVE-2020-1066
  A remote code execution vulnerability exists in .NET Framework software when the software fails to check the source markup of a file. An attacker who successfully exploited the vulnerability could run arbitrary code in the context of the current user. If the current user is logged on with administrative user rights, an attacker could take control of the affected system. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights. Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights. Exploitation of the vulnerability requires that a user open a specially crafted file with an affected version of .NET Framework. In an email attack scenario, an attacker could exploit the vulnerability by sending the specially crafted file to the user and convincing the user to open the file. The security update addresses the vulnerability by correcting how .NET Framework checks the source markup of a file.To learn more about the vulnerabilities, go to the following Common Vulnerabilities and Exposures (CVE).
• CVE-2020-0605
  A denial of service vulnerability exists when .NET Framework improperly handles web requests. An attacker who successfully exploited this vulnerability could cause a denial of service against a .NET Framework web application. The vulnerability can be exploited remotely, without authentication. A remote unauthenticated attacker could exploit this vulnerability by issuing specially crafted requests to the .NET Framework application. The update addresses the vulnerability by correcting how the .NET Framework web application handles web requests.To learn more about the vulnerabilities, go to the following Common Vulnerabilities and Exposures (CVE).
• CVE-2020-1108

Known issues in some parts of this update

Symptom| This update does not install, and it returns either or both of the following error messages:

• -2146762495
• A required certificate is not within its validity period when verifying against the current system clock or the timestamp in the signed file.
• The revocation function was unable to check revocation because the revocation server was offline.
  —|—
  Workaround| This issue was corrected by the latest release of the affected parts in this update.If you’ve already installed a previous release of the affected parts, no action is required.

Additional information about this update

The following articles contain additional information about this update as it relates to individual product versions.

• 4552965 Description of the Security Only Update for .NET Framework 3.5.1 for Windows 7 SP1 and Windows Server 2008 R2 SP1 (KB4552965)
• 4552952 Description of the Security Only Update for .NET Framework 4.5.2 for Windows 7 SP1 and Windows Server 2008 R2 SP1 and Windows Server 2008 SP2 (KB4552952)
• 4552951 Description of the Security Only Update for .NET Framework 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2 for Windows 7 SP1 and Windows Server 2008 R2 SP1 and Windows Server 2008 SP2 (KB4552951)
• 4552953 Description of the Security Only Update for .NET Framework 4.8 for Windows 7 SP1 and Windows Server 2008 R2 SP1 (KB4552953)

Information about protection and security

• Protect yourself online: Windows Security support
• Learn how we guard against cyber threats: Microsoft Security