This vulnerability (CVE-2026-50428) is an out-of-bounds read in the Windows Container Isolation FS Filter Driver (unionfs.sys) in Windows 11 version 26H1 (build 10.0.28000.0). It permits an authorized attacker with local access to read memory outside the intended bounds, potentially disclosing sensitive information. The vulnerability has a CVSS 3.1 base score of 7.1, indicating high severity, with impact primarily on confidentiality and availability. Microsoft has released an official fix for this vulnerability as documented in their security update guide.

An authorized local attacker can exploit this vulnerability to read memory beyond intended boundaries, leading to potential disclosure of sensitive information (confidentiality impact is high). The vulnerability also impacts system availability. There are no known exploits in the wild at this time.

Microsoft has provided an official fix for this vulnerability. It is recommended to apply the security update available from Microsoft as detailed in their advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-50428. No additional mitigation steps are indicated by the vendor.