Windows 11 update install

Windows 11 build 22000.1100 (KB5020387) out-of-band update fixes network bug

Microsoft pushes out-of-band updates for Windows 11 and 10 to a specific networking issue.

  • Microsoft releases out-of-band update KB5020387 for Windows 11.
  • Windows 10 is getting the KB5020435 update.
  • These two updates fix the same networking problem.

Microsoft has released the update KB5020387 as an out-of-band update for Windows 11 to address a critical vulnerability issue. At the same time, the company is also releasing the same patch as update KB5020435 for Windows 10 21H2, 21H1, and 20H2.

The update KB5020387 bumps the version number to build 22000.1100 for Windows 11, and the update KB5020435 bumps the version number to 19042.2132 (20H2), 19043.2132 (21H1), and 19044.2132 (21H2) for Windows 10.

According to the announcement (link 2), it only addresses an issue that affects some types of Secure Sockets Layer (SSL) and Transport Layer Security (TLS) connections that might have handshake failures. For developers, the affected connections will likely receive one or more records followed by a partial record with a size of fewer than five bytes within a single input buffer. If the connection fails, the app will receive the error “SEC_E_ILLEGAL_MESSAGE.”

This problem only affects the original version of Windows 11 (version 21H2), not version 22H2, and the three most releases of Windows 10.

Download update KB5020387 for Windows 11

The update is available immediately and will download and install automatically. However, you can always force the update from Settings Windows Update, click the Check for updates button, and use the option to install the update. On Windows 10, the option to update is on Settings Update & Security > Windows Update.

About the author

Mauro Huculak is a Windows expert and the Editor-in-Chief who started Pureinfotech in 2010 as an independent online publication. He is also been a Windows Central contributor for nearly a decade. Mauro has over 12 years of experience writing comprehensive guides and creating professional videos about Windows, software, and related technologies, including Android and Linux. Before becoming a technology writer, he was an IT administrator for seven years. In total, Mauro has over 20 years of combined experience in technology. Throughout his career, he achieved different professional certifications from Microsoft (MSCA), Cisco (CCNP), VMware (VCP), and CompTIA (A+ and Network+), and he has been recognized as a Microsoft MVP for many years. You can follow him on X (Twitter), YouTube, LinkedIn and