Infographic showing SMBv1 breakage from September 2025 Windows updates: affected systems (Windows 11/10, Servers), security risks (EternalBlue/WannaCry icons), workarounds (PowerShell code snippet), and migration path to SMBv2/3 with network icons.

Microsoft's September 2025 security updates have disrupted SMBv1 share connectivity over NetBIOS over TCP/IP (NetBT) in Windows clients and servers, affecting legacy-dependent systems. SMBv1, a 1983 file-sharing protocol deprecated since 2014 for SMBv2/3's superior security and performance, persists in some environments despite risks like weak encryption and exploits (e.g., EternalBlue in WannaCry/NotPetya). The updates, part of Patch Tuesday fixing 81 vulnerabilities including two zero-days, target Windows 11 (24H2/23H2/22H2), Windows 10 (22H2/21H2), and Servers (2025/2022)—issues arise in mixed updated/unupdated setups.

Infographic showing SMBv1 breakage from September 2025 Windows updates: affected systems (Windows 11/10, Servers), security risks (EternalBlue/WannaCry icons), workarounds (PowerShell code snippet), and migration path to SMBv2/3 with network icons.Infographic showing SMBv1 breakage from September 2025 Windows updates: affected systems (Windows 11/10, Servers), security risks (EternalBlue/WannaCry icons), workarounds (PowerShell code snippet), and migration path to SMBv2/3 with network icons.

This breakage highlights SMBv1's dangers: no integrity checks, unencrypted traffic, and vulnerability to ransomware like TrickBot/Emotet. Organizations facing downtime must apply workarounds like re-enabling SMBv1 via PowerShell (Set-ItemProperty -Path "HKLM:\SYSTEM\CurrentControlSet\Services\LanmanWorkstation\Parameters" EnableSecuritySignature -Value 0 -Type DWord), but this exposes systems—temporarily disable updates or use SMBv2+ compatibility modes.

Infographic showing SMBv1 breakage from September 2025 Windows updates: affected systems (Windows 11/10, Servers), security risks (EternalBlue/WannaCry icons), workarounds (PowerShell code snippet), and migration path to SMBv2/3 with network icons.Infographic showing SMBv1 breakage from September 2025 Windows updates: affected systems (Windows 11/10, Servers), security risks (EternalBlue/WannaCry icons), workarounds (PowerShell code snippet), and migration path to SMBv2/3 with network icons.

User feedback reports widespread frustration in enterprises with old hardware/printers, urging migration to modern protocols. Long-term, disable SMBv1 (via Windows Features or registry: fscache on HKLM:\SYSTEM\CurrentControlSet\Services\LanmanServer\Parameters\RequireSecuritySignature=1), audit networks, and upgrade infrastructure to avoid risks while restoring access.
 
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