Microsoft outs Windows 11 OOB update (KB5020387) to fix TLS/SSL network issues

Windows Update for Windows 11

Microsoft has released an out-of-band (OOB) update KB5020387 (Build 22000.1100) to fix the Transport Layer Security (TLS)/ Secure Sockets Layer (SSL) handshake failure issue that users are reporting. The bug is leading to failure of connection establishment between clients and servers. These were set off by this month's Patch Tuesday for both Windows 11 and Windows 10.

Here is the changelog for the new KB5020387 OOB update that fixes the TLS/SSL handshake issue on Windows 11 21H2:

Highlights

  • 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”.

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”.

To download this update, apply any available Windows update or head over to the Microsoft Update Catalog website.

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