Windows 10 KB5073724 is January 2026’s Extended Security Update (ESU) and it removes old modem drivers

Windows 10 KB5073724 is the Extended Security Update (ESU) for January 2026, available to ESU subscribers to receive security updates until October 2026 with no major changes. The update removes old modem drivers, affecting specific modem hardware relying on drivers like agrsm64.sys and smserial.sys. Additionally, new Secure Boot certificates are included to replace expired ones, ensuring PC security during startup. Microsoft also updated WinSqlite3.dll for better security and advises updating apps flagged as vulnerable. No new issues are reported with this update, as Windows 10 is in the Extended Security Updates phase.