The January 2026 security update for Windows 11, identified as KB5074109, removed certain legacy modem drivers, leading to inoperability for some users.
Drivers Removed
Specific modem drivers were eliminated in this update, including agrsm64.sys (x64), agrsm.sys (x86), smserl64.sys (x64), and smserial.sys (x86). These drivers were essential for operating older modems, leading to immediate functionality issues. Microsoft confirmed this action aimed to address unpatched security vulnerabilities associated with these drivers.
User Impact
Many users reported modem failures on Microsoft forums following the update. Some users have temporarily restored modem functionality by uninstalling the update. However, modem manufacturers have yet to supply new drivers, exacerbating the problem for those reliant on legacy systems for tasks such as phone answering and logging.
Options for Affected Users
- Uninstall update KB5074109 to potentially restore modem operation.
- Pause or disable Windows Update to prevent automatic reinstallation of the update.
- Stay informed about driver updates from modem manufacturers.
It’s important to note that operating without these updates increases vulnerability to security threats. Users must weigh the risks of unsecured systems against operational needs.
