CVE-2026-97787ImportantEoPLocal
Windows Container Isolation FS Filter Driver (unionfs.sys) Elevation of Privilege Vulnerability
Assessment
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.
- Severity
- Important
- CVSS base score
- 7.0CVSS:3.1/
AV:L/ AC:H/ PR:L/ UI:N/ S:U/ C:H/ I:H/ A:H/ E:U/ RL:O/ RC:C - Impact
- Elevation of Privilege
- EPSS, next 30 days
- Not scored yet
- Public exploit code
- No Nuclei template lists it
- Exploitability
- Exploitation Less Likely
- Publicly disclosed
- No
- Customer action
- Required: apply the update
- Component
- Windows Container Isolation FS Filter Driver (unionfs.sys)
- Weakness
- CWE-362: Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
- Issued by
- Microsoft
- Published
- 13 Oct 2026 · October 2026
- Last revised
- 13 Oct 2026
CVSS 3.1 base metricsRed raises the risk · green lowers it
- Attack vector
- LocalAV:L
- Attack complexity
- HighAC:H
- Privileges required
- LowPR:L
- User interaction
- NoneUI:N
- Scope
- UnchangedS:U
- Confidentiality
- HighC:H
- Integrity
- HighI:H
- Availability
- HighA:H
Updates that fix it
5 KBs| KB | Type | Restart | Applies to | Other CVEs |
|---|---|---|---|---|
| KB5126646 | Security Update | Required | Windows Server 2025, Windows Server 2025 (Server Core installation) | All CVEs in KB5126646 |
| KB5126653 | Security Update | Required | Windows 11 Version 23H2 for ARM64-based Systems, Windows 11 Version 23H2 for x64-based Systems | All CVEs in KB5126653 |
| KB5126655 | Security Update | Required | Windows Server 2022, Windows Server 2022 (Server Core installation) | All CVEs in KB5126655 |
| KB5127646 | Security Update | Required | Windows 11 Version 26H1 for ARM64-based Systems, Windows 11 version 26H1 for x64-based Systems | All CVEs in KB5127646 |
| KB5127648 | Security Update | Required | Windows 11 Version 24H2 for ARM64-based Systems, Windows 11 Version 24H2 for x64-based Systems, Windows 11 Version 25H2 for ARM64-based Systems and 3 more | All CVEs in KB5127648 |
Affected products
Windows14 affected products
- Windows 11 Version 23H2 for ARM64-based Systems
- Windows 11 Version 23H2 for x64-based Systems
- Windows 11 Version 24H2 for ARM64-based Systems
- Windows 11 Version 24H2 for x64-based Systems
- Windows 11 Version 25H2 for ARM64-based Systems
- Windows 11 Version 25H2 for x64-based Systems
- Windows 11 Version 26H1 for ARM64-based Systems
- Windows 11 version 26H1 for x64-based Systems
- Windows 11 Version 26H2 for ARM64-based Systems
- Windows 11 Version 26H2 for x64-based Systems
- Windows Server 2022
- Windows Server 2022 (Server Core installation)
- Windows Server 2025
- Windows Server 2025 (Server Core installation)
What changed
First observed 14 Oct 2026No field changes in the recorded history.
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