Windows 11 Update Causes Critical System Drive Access Issues on Samsung Devices
Microsoft has officially acknowledged a significant issue affecting Windows 11 users, particularly those operating Samsung devices. Following the installation of the February 2026 security update (KB5077181, OS Build 26100.7840), users have reported complete inaccessibility to their system drive (C:), rendering essential applications and system functions unusable.
Issue Overview
After applying the February 2026 Patch Tuesday update, affected Samsung devices display the error message: C:\ is not accessible – Access denied. This error effectively locks users out of their system drive, preventing the launch of applications such as Microsoft Outlook, Office suite, web browsers, and system utilities. Even basic administrative tasks become impossible, as users are unable to elevate privileges, uninstall updates, or collect diagnostic logs due to cascading permission failures.
Scope of Impact
The problem predominantly affects Samsung Galaxy Book 4 and other Samsung consumer devices. Reports have emerged from various regions, including Brazil, Portugal, South Korea, and India. The affected Windows versions are Windows 11 version 25H2 and Windows 11 version 24H2; no server platforms are currently impacted.
Enterprise administrators have also flagged the problem on Reddit’s r/sysadmin community, noting that affected Galaxy Book laptops within Active Directory domains cannot have NTFS permissions modified, even using administrator credentials. Secondary failures reported include trackpad driver malfunctions and the inability to open PowerShell, as its binary resides on the now-inaccessible C: drive.
Potential Cause
Microsoft’s investigation points to the Samsung Share application as a probable contributing factor, though the root cause has not yet been fully validated. The issue is believed to involve corrupted or incorrectly applied Access Control Lists (ACLs) on the root of the system drive.
Current Status and Recommendations
As of March 13, 2026, Microsoft has classified the issue as Investigating and has not yet released an official fix or workaround. A Reddit user claiming to be a Samsung technician in Brazil posted an unofficial workaround involving reassigning C: drive ownership to the Everyone group. However, Microsoft security experts strongly caution against this approach, as it strips Windows’ built-in security protections from critical system directories.
Microsoft has advised affected users to wait for an official patch and has committed to providing further updates as the investigation progresses.
