Windows September Update Breaks SMBv1
Introduction
Microsoft’s September 2023 Patch Tuesday updates introduced important security and performance enhancements—but not without some critical side effects. With the rollout of these cumulative updates, Windows users began to report a significant issue: the inability to access shared folders over SMBv1 (Server Message Block version 1). Microsoft has since confirmed the bug, noting that certain legacy systems leveraging SMBv1 are now broken as a result of the update.
What is SMBv1 and Why It Matters
SMBv1 is a network file sharing protocol that dates back to the 1980s. While superseded by more secure and efficient versions like SMBv2 and SMBv3, some older network devices—including legacy NAS units and embedded IoT systems—still rely on SMBv1 for file and printer sharing capabilities.
Security experts have long advised companies to phase out SMBv1 usage, particularly after its vulnerabilities were exploited in the infamous WannaCry ransomware attack in 2017. Despite the risks, SMBv1 remains in use within legacy environments where upgrades aren’t always feasible.
Issue Introduced by the September Update
According to Microsoft’s official documentation, after installing the September 2023 cumulative updates on Windows 10 or Windows 11, users might encounter problems accessing SMBv1 shared folders. The issue typically results in the following symptoms:
- Inability to connect to specific shares via file explorer or mapped drives.
- Unexpected error messages like “The network path was not found.”
- Failure of legacy applications that rely on SMBv1 communication.
Microsoft clarified that the bug primarily affects client systems and has not impacted SMB servers running newer versions of the protocol (SMBv2/3).
Microsoft’s Acknowledgment and Guidance
Microsoft has officially acknowledged the bug and added it to the list of known issues related to the September update. While there is no permanent fix at the time of writing, Microsoft has offered a temporary workaround:
- Reboot the SMBv1 server device. In many cases, this temporarily restores access to the shared folders.
- Use newer versions of SMB wherever possible to minimize dependency on unsupported protocols.
Microsoft emphasized again that SMBv1 is deprecated and should be avoided for both security and compatibility reasons. Enterprises still relying on SMBv1 are encouraged to migrate to more modern solutions.
Impact on Enterprises and Legacy Devices
Organizations with legacy infrastructure may face immediate disruption due to this SMBv1 issue. Devices such as:
- Older Network Attached Storage (NAS) units
- Industrial control hardware
- Embedded IoT devices
may suddenly become unavailable to modern Windows clients following the September update. IT administrators are now under pressure to create temporary workarounds or accelerate upgrade timelines for incompatible hardware.
Best Practices Going Forward
If your business is still dependent on SMBv1, it may be time to consider more long-term solutions. Here are some practical recommendations:
- Conduct an internal audit to identify all systems and devices using SMBv1.
- Apply segmentation to isolate legacy systems from the rest of the network.
- Upgrade or replace legacy hardware where SMBv2/3 support is not available.
- Monitor Microsoft’s updates for a formal fix or patch addressing the SMBv1 share bug.
Final Thoughts
The September 2023 Windows update highlights the growing tension between innovation and legacy support. While Microsoft’s move to phase out SMBv1 is guided by strong security motivations, the unintended hiccups from this update serve as a wake-up call for organizations lagging behind in tech modernization.
Until a long-term fix is provided, businesses should leverage the suggested workarounds—but more importantly, start planning to retire SMBv1 from their networks entirely.