Microsoft released out-of-band updates for Windows 11 and 10

Microsoft has released two out-of-band patches for actual Windows versions. Windows 10 receives KB5020435 to fix issues with SSL and TLS, and Windows 11 is getting KB5020387, Build 22000.1100, that resolves the same issues.

• KB5020435 is available for Windows 10 20H2, 21H1, and 21H2. OS Builds 19042.2132, 19043.2132, and 19044.2132.
• KB5020387 is available for the original Windows 11 release. OS Build 22000.1100

The updates fix the following issue:

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 are a Windows 10 user, keep in mind that its patch comes with known issues.

First of all, on certain configurations it may prevent audio from working. If your device is affected, you can apply this known issue rollback option.

Second, if you are using a custom built ISO image, you need to update it with the latest servicing stack update before slipstreaming KB5020435. Otherwise it may remove Edge Legacy but won't add Edge Chromium.

You will find the patches in the Settings app (Win + I) under the Windows Update section. Alternatively, you can download them from the Microsoft Update Catalog website, here.