Having Trouble Accessing Network Shares? A Recent Windows Update Might Be the Culprit
If you’ve recently installed the latest Windows updates and are now suddenly facing “access denied” errors when trying to connect to a network share, you are not alone. A known issue in the September 2023 cumulative updates for Windows 10 and Windows 11 is causing significant problems for users attempting to access shares hosted on servers using the older SMBv1 protocol.
Microsoft has officially acknowledged the problem, which is preventing users from connecting to network resources that they could previously access without issue. This guide breaks down what’s happening, why it’s a security concern, and what you can do about it.
The Problem: “Access Denied” After September 2023 Updates
Users have reported that after installing recent updates, attempts to access certain network file shares result in an immediate failure. The most common symptom is the error code 0x80070005, which signifies “Access is denied.”
This issue has been directly linked to the following cumulative updates:
- KB5029263 for Windows 11 22H2
- KB5029244 for Windows 10 22H2
The problem specifically affects client devices that have been updated and are trying to connect to a server or device that relies on the SMBv1 network protocol. This is common in environments with legacy hardware, such as older Network Attached Storage (NAS) devices, multifunction printers, or specialized industrial equipment.
Microsoft has confirmed the issue and is actively investigating it. A permanent fix is expected to be delivered in a future software release.
Why This Is Happening: The Insecurity of SMBv1
While the connection issue is an unintended consequence of the update, it highlights a critical security topic: the Server Message Block version 1 (SMBv1) protocol.
SMBv1 is a deprecated and dangerously insecure protocol. It was first developed in the 1980s and lacks the modern security features found in its successors, SMBv2 and SMBv3. Its vulnerabilities are well-documented and have been exploited by some of the most infamous cyberattacks in history, including the WannaCry and NotPetya ransomware worms.
For years, Microsoft has been strongly advising all users and administrators to disable SMBv1 and migrate to modern versions. The recent update likely introduced a security hardening measure that, as a side effect, broke compatibility with the outdated protocol.
What You Can Do Now: Solutions and Security Best Practices
While waiting for an official patch from Microsoft, you have a few options. However, the best course of action focuses on long-term security rather than short-term convenience.
1. The Long-Term Solution: Migrate Away from SMBv1
This incident should serve as a powerful reminder to audit your network and eliminate any reliance on SMBv1. This is the most secure and permanent solution.
- Identify Legacy Devices: Scan your network to find any servers, NAS devices, or printers that are still configured to use SMBv1.
- Update Firmware: Check with the device manufacturer for firmware updates. Most modern devices support SMBv2 or SMBv3, and a simple update may be all that is needed to enable it.
- Reconfigure or Replace: If a device cannot be updated to a newer SMB version, you should reconfigure it or create a plan to replace it as soon as possible. Continuing to use hardware that relies on SMBv1 exposes your network to significant risk.
2. The Temporary Workaround (Use with Caution)
For business-critical systems where access is immediately required, you might consider uninstalling the latest cumulative update. To do this, go to Settings > Windows Update > Update history > Uninstall updates and remove the relevant KB number.
Warning: This should be a last resort. Uninstalling a cumulative update will also remove all the security patches it contains, leaving your system vulnerable to other known exploits. If you must do this, ensure you have other compensating security controls in place and reinstall the update as soon as a permanent fix is available.
In summary, while Microsoft is working to resolve the immediate access issue, the root cause lies in the continued use of an obsolete protocol. Use this opportunity to enhance your network security by identifying and upgrading any systems still dependent on SMBv1.
Source: https://www.bleepingcomputer.com/news/microsoft/microsoft-says-windows-september-updates-break-smbv1-shares/
