A newly discovered issue in Windows 11 is creating major problems for some PC users, with Samsung laptop owners appearing to be among the most affected. Microsoft has acknowledged reports that certain computers can lose access to their main system drive after installing a recent security update released in February 2026.

When the problem occurs, users are greeted with an error stating that the C drive cannot be accessed due to denied permissions. Because the C drive typically stores the Windows operating system along with most applications and files, the error can severely limit what the computer is able to do.

Microsoft says it is currently investigating the situation and is working with Samsung to understand what is causing the behaviour. For users experiencing the issue, the malfunction can make their devices difficult or impossible to use normally.

Reports indicate the problem is most commonly affecting Samsung consumer laptops, particularly models in the Galaxy Book 4 line-up running Windows 11 versions 24H2 or 25H2. Cases have also been observed in several countries including India, Brazil, Portugal and South Korea, suggesting the bug is not confined to a single region.

Early findings suggest a possible connection with the Samsung Share application, although Microsoft has not confirmed this as the definitive cause. The issue appears after installing the February 2026 Patch Tuesday security update identified as KB5077181, which corresponds to operating system build 26100.7840.

The malfunction does not appear to require any unusual action from the user. Instead, it may occur during everyday tasks such as opening files, launching applications or carrying out system administration functions. When the bug appears, Windows may suddenly block access to the system drive, preventing programs and files from being opened.

The consequences can extend beyond a simple access error. Some affected systems are unable to run commonly used applications including Microsoft Outlook, Office programs, web browsers and other built-in Windows tools because they rely on files stored on the main system drive.

In certain situations, the permissions issue can also prevent users from performing maintenance tasks such as uninstalling updates, collecting diagnostic information or granting administrative privileges.

Some users have shared potential workarounds online, including manually adjusting ownership permissions for the entire C drive. However, experts warn that altering these permissions could compromise Windows security protections and potentially expose the system to additional risks.

Microsoft has not yet released an official fix for the issue. The company says it is continuing to analyse reports in collaboration with Samsung and will provide further guidance once the root cause has been identified.