CVE-2026-84009: Windows Projected File System Tampering Vulnerability
Time-of-check time-of-use (toctou) race condition in Windows Projected File System allows an authorized attacker to perform tampering locally.
Other sources
Windows Projected File System Tampering 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 10.0.17763.9376Patch KB5126651 - Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 10.0.19044.7807Patch KB5126657 - Upgrade
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Fixed in 10.0.26100.9711Patch 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 10.0.26300.9711Patch 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 10.0.26100.33650Patch 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 10.0.20348.5761Patch KB5126655
Event History
Frequently Asked Questions
What access does an attacker need to exploit this issue?
The attacker must already be authorized to access the affected system locally and must have low privileges. Exploitation does not require user interaction, but the race condition has high attack complexity.
Which systems are identified as affected?
The affected software list includes Microsoft Windows 10, Windows 11, Windows Server 2019, Windows Server 2022, and Windows Server 2025.