CVE-2026-50428
High CVSS 7.1Published 2026-07-14 ยท last changed 2026-07-22
The fix
Microsoft fixes this in updateKB5101649. The fixed build differs per Windows version, so the row that matters is the one matching the machine you are looking at.
| Windows version | Fixed in build | Update | Released |
|---|---|---|---|
| Windows 11 Version 26H1 for ARM64-based Systems | 10.0.28000.2525 | KB5101649 | 2026-09-20 |
| Windows 11 version 26H1 for x64-based Systems | 10.0.28000.2525 | KB5101649 | 2026-09-20 |
Having the KB is not the same as knowing whether a machine has it. Windows updates supersede each other, so the update you installed often covers a fix that shipped in an earlier one. Paste your build into the patch checker and it walks that chain for you.
What it is
Out-of-bounds read in Windows Container Isolation FS Filter Driver (unionfs.sys) allows an authorized attacker to disclose information locally.
Sources
CVSS vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H