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

The update fixes a connection issue that throws “SEC_E_ILLEGAL_MESSAGE” error. Here is the full changelog of update KB5020387 in terms of new features, fixes and improvements.

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

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

If you installed earlier updates, only the new updates contained in this package will be downloaded and installed on your device.

Download link:

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