September Patch Tuesday Update KB5065426 Breaks File and Print Sharing

Windows 11’s September Patch Tuesday update, KB5065426, is reportedly breaking file and print sharing across networks. According to posts on the Microsoft Community forum, the latest update is disabling sharing options and switching networks from private to public without warning.

IT admins say that even after restoring the settings, sharing remains broken. In many cases, the only way to get functionality back has been to uninstall the update. One user described the situation as “chaos,” noting that thousands of computers in their company could no longer access shared printers or files.

Other reports mention login issues when accessing shared folders. That too, even with correct credentials, Windows is rejecting usernames and passwords as invalid, leaving an error message “The username or password is incorrect.”

While the exact cause of this issue is unknown, some hint at the fault to user SIDs, with duplicate SIDs blocking authentication until new users are created or the system is reset with Sysprep.

The issue is even worse for those who rely on file and print sharing in offices, schools, and enterprises. Microsoft has yet to comment on this matter. At the time of writing, Microsoft has not issued an official fix or workaround beyond uninstalling KB5065426.

We advise users who depend heavily on file and print sharing to hold off installing the update until further clarification arrives.