Download link & Changelog: Windows 11 update KB5020387

Microsoft has now released an out-of-band update KB5020387 (Build 22000.1100) for all devices running Windows 11 version 21H2. Update KB5020387 brings an important fix.

The update fixes a connection issue that is causing the “SEC_E_ILLEGAL_MESSAGE” error to appear. Here is the complete change of update KB5020387 in terms of new features, fixes and improvements.

This non-security update includes quality improvements. The main changes include:

  • We are addressing an issue that may affect some types of Secure Sockets Layer (SSL) and Transport Layer Security (TLS) connections. These connections may have a handshake failure. For developers, affected connections will likely receive one or more records followed by a partial record of less than 5 bytes within a single input buffer. If the connection fails, your app will receive the “SEC_E_ILLEGAL_MESSAGE” error.

If you have installed previous updates, only the new updates included in this package will be downloaded and installed on your device.

Download Link:

You can download and install Windows 11 update KB5020387 manually by clicking here. If you need help understanding how to install these updates manually on your computer, you can refer to our handy step-by-step tutorial.