CVE-2026-97787: Windows Container Isolation FS Filter Driver (unionfs.sys) Elevation of Privilege Vulnerability
Concurrent execution using shared resource with improper synchronization ('race condition') in Windows Container Isolation FS Filter Driver (unionfs.sys) allows an authorized attacker to elevate privileges locally.
Other sources
Windows Container Isolation FS Filter Driver (unionfs.sys) Elevation of Privilege Vulnerability
— Microsoft
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 10.0.26300.9711Patch KB5127648 - Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 10.0.26100.33650Patch KB5126646 - Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 10.0.26200.9711Patch KB5127648 - Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 10.0.22631.7652Patch KB5126653 - Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 10.0.26100.9711Patch KB5127648 - Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 10.0.28000.3231Patch KB5127646 - Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 10.0.20348.5761Patch KB5126655
Event History
Frequently Asked Questions
Who is exposed to this vulnerability?
Systems running the affected Microsoft Windows 11, Windows Server 2022, or Windows Server 2025 software, including the Windows Container Isolation FS Filter Driver (unionfs.sys), are in scope.
What does an attacker need to exploit it?
An attacker needs local authorized access with low privileges. Exploitation requires winning a race condition involving concurrent use of a shared resource; no user interaction is required.
What is the potential impact if exploitation succeeds?
A successful exploit can elevate the attacker’s privileges locally. The provided severity vector indicates high potential impact to confidentiality, integrity, and availability.