Microsoft Windows Cross Device Service Elevation of Privilege Vulnerability

Improper access control in Windows Cross Device Service allows an authorized attacker to elevate privileges locally.

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7.8CVSS out of 10High severity

Scope

What the vendor says is affected

Windows 10 Version 22H2 for x64-based Systems
Windows 10 Version 22H2 for ARM64-based Systems
Windows 10 Version 22H2 for 32-bit Systems
Windows 11 Version 25H2 for ARM64-based Systems
Windows 11 Version 25H2 for x64-based Systems
Windows 11 Version 24H2 for ARM64-based Systems
Windows 11 Version 24H2 for x64-based Systems
Windows 11 version 26H1 for x64-based Systems
Windows 11 Version 26H1 for ARM64-based Systems

Versions the vendor lists as fixed

10.0.19045.7663
10.0.26200.9168
10.0.26200.9106
10.0.26100.9168
10.0.26100.9106
10.0.28000.2704

Next step

What the vendor recommends

Install KB5120249. Install KB5121003. Install KB5120994. Install KB5121000.

Review the complete instructions on the vendor's site

Update history

What changed in later vendor updates

SecurityAlert records field-level changes from the point we begin following a bulletin. Earlier vendor changes may not have a field-by-field record.

Aug 27, 2026 at 3:15 PM UTC
- The vendor changed the advisory's last-updated date.
Aug 20, 2026 at 7:00 PM UTC
- The vendor changed its remediation guidance.

Timeline

When this advisory changed

Aug 11, 2026 at 7:00 AM UTC
Published by Microsoft Security Response Center
The publication date reported by the vendor.
Aug 20, 2026 at 6:50 PM UTC
Added to SecurityAlert
We collected the advisory from the official source.
Aug 27, 2026 at 7:00 AM UTC
Updated by Microsoft Security Response Center
The vendor changed the advisory after it was first published.
Sep 2, 2026 at 5:15 PM UTC
Confirmed at the source
Our collector saw this advisory during a later source check.

Vulnerabilities

CVEs named in this advisory

CVE-2026-66804View 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-2026-66804
Last source check: Sep 13, 2026 at 2:40 AM UTC

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What the vendor says is affected

Versions the vendor lists as fixed

What the vendor recommends

What changed in later vendor updates

When this advisory changed

CVEs named in this advisory

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