TLS/SSL handshakes break across all Windows

October’s update broke TLS and SSL across every supported Windows version simultaneously. Encrypted connections would fail when receiving a record followed by a partial record smaller than 5 bytes. Citrix clients couldn’t talk to NetScalers. Enterprise HTTPS applications dropped connections. Every single actively supported Windows release was affected — that’s some impressive regression coverage. Microsoft needed emergency OOB patches within a week to restore the ability to do HTTPS, which in 2022 was approximately all web traffic.