Microsoft Confirms Windows 11 Bug That Locks Users Out of the C: Drive

Microsoft has confirmed a Windows 11 bug that can block access to the system drive after installing the February 2026 Patch Tuesday update KB5077181. The issue appears mainly on Samsung laptops and can prevent users from accessing files or launching applications.

Issue emerges after the February Patch Tuesday update

KB5077181 was released about a month ago as part of the February Patch Tuesday rollout. When the update first arrived, users reported a wide range of problems, including boot loops, login errors, and installation issues.

Microsoft has now acknowledged another problem linked to the same update. Some affected users see the message “C:\ is not accessible – Access denied” when trying to open the system drive.

System access problems can make PCs difficult to use

The error blocks access to files stored on the system drive and prevents applications from launching normally. Administrative tasks may also fail because Windows cannot properly access system files.

In severe situations, the system can become almost unusable since many Windows features rely on access to the C: drive.

Samsung laptops appear to be the main devices affected

Reports have surfaced in multiple regions, including Brazil, Portugal, Korea, and India. Despite the global reports, the issue does not appear to be widespread.

Most of the cases involve Samsung consumer laptops, particularly devices such as the Samsung Galaxy Book4. Other Samsung models may also experience the problem.

Microsoft believes the issue may be related to the Samsung Share application, although the exact cause has not yet been confirmed.

Only newer Windows 11 versions are affected

The problem appears limited to Windows 11 versions 24H2 and 25H2. Systems running Windows 10 or Windows 11 version 23H2 and earlier do not appear to be affected.

Some users have attempted temporary workarounds such as changing ownership permissions of the C: drive. However, modifying system drive permissions can introduce additional problems and is not recommended for most users.

Microsoft says it is currently investigating the issue and plans to release a fix in a future update.

In related update news, Microsoft has released KB5079458 and KB5079464 for the Beta and Dev channels. These updates introduce improvements to Windows Setup and changes to the driver policy system.

Via Neowin