A fresh Windows 11 bug is causing serious headaches for some PC owners, and Samsung laptop users appear to be bearing the brunt of it. Microsoft has confirmed reports that certain devices running recent Windows 11 builds can suddenly lose access to the system drive after installing a February 2026 security update.
When the issue triggers, users see the error message “C: is not accessible – Access denied”, effectively locking them out of the drive where Windows and most applications reside. The company says it is actively investigating the issue and working with Samsung to determine the root cause. For affected users, though, the problem can render their machines partially unusable.
Why are Samsung laptops being hit the hardest?
According to Microsoft’s release health documentation, the issue has been reported mainly on Samsung consumer devices such as the Galaxy Book 4 series running Windows 11 versions 24H2 or 25H2. Add to that, it’s predominantly in regions like India, Brazil, Portugal, and South Korea, indicating the bug isn’t limited to a single market.
Early investigation suggests the bug may be connected to the Samsung Share application, though Microsoft says the root cause has not yet been fully confirmed. The problem appears after installing the February 2026 Patch Tuesday update (KB5077181), which corresponds to OS build 26100.7840. Interestingly, the failure isn’t tied to any specific user action. Instead, it can surface during routine tasks like opening files, launching apps, or performing administrative operations. Once triggered, Windows may suddenly deny permission to the system drive, breaking access to files and programs stored on it.
What actually happens when the bug strikes?
The impact goes well beyond a simple error message. Affected systems may fail to launch everyday software such as Outlook, Office apps, web browsers, and Windows utilities, because those programs rely on files stored on the C drive. In some cases, the permission issues also prevent users from elevating privileges, uninstalling updates, or even collecting diagnostic logs.
Some users online have suggested temporary workarounds, such as manually changing file ownership permissions for the entire system drive. However, doing so could weaken Windows’ built-in protections and expose the system to further risks. For now, Microsoft has not provided an official fix. The company says it is investigating the reports alongside Samsung and will share more information once the root cause is confirmed.
