Vulnerability in Microsoft Windows 10 Version 1809
CVE-2026-84009
Time-of-check time-of-use (toctou) race condition in Windows Projected File System allows an authorized attacker to perform tampering locally.
Vulnerability class: TOCTOU (Time-of-Check to Time-of-Use)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 4.7 (Medium). Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:N.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
- Microsoft Windows 10 Version 1809
- Microsoft Windows 10 Version 21h2
- Microsoft Windows 10 Version 22h2
- Microsoft Windows 11 Version 23h2
- Microsoft Windows 11 Version 24h2
- Microsoft Windows 11 Version 25h2
- Microsoft Windows 11 Version 26h1
- Microsoft Windows 11 Version 26h2
- Microsoft Windows Server 2019
- Microsoft Windows Server 2019 (Server Core Installation)
Weakness classification (CWE)
References
- msrc.microsoft.com/update-guide/vulnerability/CVE-2026-84009 (vendor-advisory, patch)
Frequently asked questions
- What is CVE-2026-84009?
- CVE-2026-84009 is a medium-severity vulnerability in Microsoft Windows 10 Version 1809, classified under Time-of-check Time-of-use (TOCTOU) Race Condition. CVSS score: 4.7/10. Published 2026-10-13.
- How severe is CVE-2026-84009?
- Medium severity. CVSS v3 base score is 4.7 out of 10.