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Windows September 2025 updates cause SMBv1 connection issues

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📰 1 unique sources, 1 articles

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Microsoft's September 2025 Windows security updates are causing connection issues with Server Message Block (SMB) v1 shares. The problem affects multiple Windows client and server platforms, including Windows 11, Windows 10, Windows Server 2025, and Windows Server 2022. The issue arises when connecting to SMBv1 shares over the NetBIOS over TCP/IP (NetBT) protocol. Microsoft has provided a temporary workaround to resolve the issue until a permanent fix is available. The workaround involves allowing traffic on TCP port 445, which switches the SMB connection to use TCP instead of NetBT. The SMBv1 protocol has been deprecated since 2014 and is no longer installed by default in recent Windows versions. Microsoft has long advised against using SMBv1 due to its security vulnerabilities, which include susceptibility to man-in-the-middle attacks and lack of pre-authentication integrity checks.

Timeline

  1. 15.09.2025 15:48 📰 1 articles · ⏱ 7h ago

    Microsoft confirms September 2025 updates break SMBv1 connections

    Microsoft's September 2025 Windows security updates are causing connection issues with SMBv1 shares over the NetBT protocol. The issue affects multiple Windows client and server platforms. A temporary workaround has been provided to allow traffic on TCP port 445, switching the SMB connection to use TCP instead of NetBT. The SMBv1 protocol has been deprecated since 2014 and is known for its security vulnerabilities.

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