Windows Projected File System Elevation of Privilege Vulnerability

Use after free in Windows Projected File System allows an authorized attacker to elevate privileges locally.

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7.0CVSS out of 10High severity

Scope

What the vendor says is affected

Windows 10 Version 1809 for 32-bit Systems
Windows Server 2022
Windows 10 Version 21H2 for ARM64-based Systems
Windows 10 Version 21H2 for x64-based Systems
Windows Server 2022 (Server Core installation)
Windows Server 2019
Windows Server 2019 (Server Core installation)
Windows 10 Version 1809 for x64-based Systems
Windows 10 Version 22H2 for x64-based Systems
Windows 10 Version 21H2 for 32-bit Systems
Windows 10 Version 22H2 for ARM64-based Systems
Windows 10 Version 22H2 for 32-bit Systems
Windows Server 2025 (Server Core installation)
Windows 11 Version 25H2 for x64-based Systems
Windows 11 Version 23H2 for ARM64-based Systems
Windows 11 Version 23H2 for x64-based Systems
Windows 11 Version 25H2 for ARM64-based Systems
Windows Server 2022, 23H2 Edition (Server Core installation)
Windows Server 2025
Windows 11 Version 24H2 for x64-based Systems
Windows 11 Version 24H2 for ARM64-based Systems
Windows 11 version 26H1 for x64-based Systems
Windows 11 Version 26H1 for ARM64-based Systems

Versions the vendor lists as fixed

10.0.17763.8755
10.0.20348.5139
10.0.20348.5074
10.0.19044.7291
10.0.19045.7417
10.0.26100.32860
10.0.26100.32772
10.0.26200.8457
10.0.26200.8390
10.0.22631.7079
10.0.22631.7219
10.0.25398.2330
10.0.26100.8457
10.0.26100.8390
10.0.28000.2113

Next step

What the vendor recommends

Install KB5087538. Install KB5087545. Install KB5087424. Install KB5087544. Install KB5094127. Install KB5087539. Install KB5087423. Install KB5089549. Install KB5089466. Install KB5087420. Install KB5093998. Install KB5087541. Install KB5089548.

Review the complete instructions on the vendor's site

Timeline

When this advisory changed

May 12, 2026 at 7:00 AM UTC
Published by Microsoft Security Response Center
The publication date reported by the vendor.
Sep 27, 2026 at 11:11 PM UTC
Added to SecurityAlert
We collected the advisory from the official source.

Vulnerabilities

CVEs named in this advisory

CVE-2026-34340View CVSS, KEV, EPSS, and threat context

Source

Start with the vendor's bulletin

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Vendor: Microsoft Security Response Center
Advisory ID: CVE-2026-34340
Last source check: Sep 27, 2026 at 11:11 PM UTC

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What the vendor says is affected

Versions the vendor lists as fixed

What the vendor recommends

When this advisory changed

CVEs named in this advisory

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