CVE-2026-84009
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Windows Projected File System TOCTOU Race Condition
Vulnerability report for CVE-2026-84009, including description, CVSS score, EPSS score, affected products, exploitability, helpful resources, and attack-flow context.
Publication date: 2026-10-13
Last updated on: 2026-10-13
Assigner: Microsoft Corporation
Description
Description
Time-of-check time-of-use (toctou) race condition in Windows Projected File System allows an authorized attacker to perform tampering locally.
CVSS Scores
EPSS Scores
| Probability: | |
| Percentile: |
Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| Microsoft | Windows | 10 Version 1809 10.0.17763.0 |
| Microsoft | Windows | 10 Version 21H2 10.0.19044.0 |
| Microsoft | Windows | 10 Version 22H2 10.0.19045.0 |
| Microsoft | Windows | 11 version 23H2 10.0.22631.0 |
| Microsoft | Windows | 11 Version 23H2 10.0.22631.0 |
| Microsoft | Windows | 11 Version 24H2 10.0.26100.0 |
| Microsoft | Windows | 11 Version 25H2 10.0.26200.0 |
| Microsoft | Windows | 11 version 26H1 10.0.28000.0 |
| Microsoft | Windows | 11 Version 26H2 10.0.26300.0 |
| Microsoft | Windows | Server 2019 10.0.17763.0 |
| Microsoft | Windows | Server 2019 (Server Core installation) 10.0.17763.0 |
| Microsoft | Windows | Server 2022 10.0.20348.0 |
| Microsoft | Windows | Server 2025 10.0.26100.0 |
| Microsoft | Windows | Server 2025 (Server Core installation) 10.0.26100.0 |
Helpful Resources
Exploitability
CWE
KEV
| CWE ID | Description |
|---|---|
| CWE-367 | The product checks the state of a resource before using that resource, but the resource's state can change between the check and the use in a way that invalidates the results of the check. |
