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Will the January 2026 Windows Update Break My Old Modem?
To access the January 2026 update (KB5073724), you must possess an active Extended Security Update (ESU) subscription. This cumulative update advances your operating system to Build 19045.6809. While it extends security coverage through October 2026, you will not see new features; official support for Windows 10 has ceased, and development focus remains on Windows 11.
You may install this update via Settings > Update & Security > Windows Update. Alternatively, offline installers (.msu files) are available in the Update Catalog, though these require verified ESU status to initialize.
Deprecation of Legacy Modem Drivers
Microsoft has permanently removed specific legacy drivers to streamline system security. While this change affects a negligible percentage of users, you should verify your hardware if you utilize vintage networking equipment.
The update removes support for the following drivers:
- Agere (formerly Lucent) / LSI chipsets: agrsm64.sys (x64) and agrsm.sys (x86)
- Motorola SM56-class hardware: smserl64.sys (x64) and smserial.sys (x86)
If your system relies on these specific drivers for internet connectivity, your modem hardware will cease to function after installation.
Critical Secure Boot Certificate Renewal
This update implements a mandatory refresh of Secure Boot certificates. Systems running Windows 10 Enterprise LTSC and ESU currently utilize certificates issued in 2011 which are reaching expiration. KB5073724 replaces these with 2023-issued certificates.
This replacement is vital. The Secure Boot feature uses these certificates within your UEFI firmware to validate the Windows boot loader during startup. Without this update, your firmware may eventually reject the boot loader, viewing it as untrusted, which leaves the system vulnerable to boot-level attacks.
WinSqlite3 and Component Security
Microsoft has patched WinSqlite3.dll to resolve known security flaws. Previously, antivirus solutions flagged applications utilizing older versions of this DLL as vulnerable. If you continue to receive security alerts regarding sqlite3.dll after this update, you must update the specific third-party app via its developer or refresh Microsoft-owned apps through the Windows Store.
Security Vulnerability Breakdown
You should prioritize this installation immediately. The January 2026 Patch Tuesday addresses 114 distinct vulnerabilities, including three zero-day threats.
Key Security Fixes:
- Elevation of Privilege (57 counts): Patches holes that allow attackers to gain administrative rights.
- Remote Code Execution (22 counts): Fixes critical flaws (6 rated Critical) where attackers could run code on your machine remotely.
- Information Disclosure (22 counts): mitigate risks including the Desktop Window Manager zero-day exploit (CVE-2026-20805), which allowed unauthorized memory reading via a remote ALPC port.
- Security Feature Bypass: Resolves the Secure Boot certificate vulnerability (CVE-2026-21265).