Executive brief
A security vulnerability exists in the Windows component responsible for managing container file systems. An attacker who already has basic access to a system could exploit this flaw to view sensitive information that should be restricted or cause a system crash. This impacts the confidentiality of data and the overall stability of Windows 11 environments using container technology.
Technical details
This vulnerability is classified as an out-of-bounds read (CWE-125) within the Windows Container Isolation FS Filter Driver (unionfs.sys). The flaw occurs when the driver improperly handles memory buffers during file system operations related to container isolation. An attacker with low-privileged local access can trigger this condition to read data from restricted memory locations or cause a system hang/crash (BSOD). The vulnerability affects Windows 11 version 26H1, and Microsoft has released security updates to address the issue.
Affected products
- Microsoft Windows 11 version 26H1 10.0.28000.0 to 10.0.28000.2269
Timeline
- 2026-07-14: disclosed
- 2026-07-14: advisory