Microsoft has rolled out the first Windows 10 update of 2026 in the form of security patch KB5073724. The update is available for systems running Windows 10 21H2, Windows 10 Enterprise LTSC 2021, and Windows 10 22H2, provided they are enrolled in Microsoft’s Extended Security Updates (ESU) program. As Windows 10 is no longer receiving feature updates, KB5073724 focuses exclusively on security and maintenance fixes.
The update bundles together security changes that Microsoft had already released in December 2025 through updates KB5071546 and KB5074976. One notable change affects legacy modem support: several older modem drivers, including agrsm64.sys, agrsm.sys, smserl64.sys, and smserial.sys, have been removed. As a result, any modem hardware that relies on these drivers will no longer function under Windows 10 after the update is installed.
KB5073724 also introduces changes related to Secure Boot. Beginning with this update, Windows quality updates now include a subset of high-confidence device targeting data that determines which systems are eligible to automatically receive new Secure Boot certificates. Microsoft says devices will only receive these certificates after enough successful update signals have been verified, allowing for a controlled and phased rollout. In addition, the core Windows component WinSqlite3.dll has been updated after some security software previously flagged it as vulnerable.
At the time of release, Microsoft has not reported any known issues that would affect most private users installing KB5073724. However, the company notes that the update could potentially cause problems in Azure Virtual Desktop and Windows 365 environments. The update is being distributed as part of the January 2026 Patch Tuesday cycle and should install automatically via Windows Update, though it can also be downloaded manually from the Microsoft Update Catalog if needed.