Microsoft's September Windows Update Disrupts SMBv1 Shares

Microsoft's September 2025 Windows security updates are causing connection problems with SMBv1 shares across various Windows platforms. The issue affects both client and server versions and occurs when either the SMB client or server has the update installed. Microsoft is working on a fix and recommends a temporary workaround by allowing traffic on TCP port 445 to restore SMB connections. SMBv1, an outdated and insecure protocol, has been deprecated and phased out due to its vulnerabilities and history of exploitation.