MSRC-CVE-2026-66804 — Microsoft Windows Cross Device Service Elevation of Privilege Vulnerability

Summary

Impact: Elevation of Privilege. Microsoft rating: Important. Not known to be exploited — Exploitation More Likely. Customer action: Required.

Details

What privileges could be gained by an attacker who successfully exploited this vulnerability?
An attacker who successfully exploited this vulnerability could gain SYSTEM privileges.

Security updates
10.0.19045.7663 — https://support.microsoft.com/help/5120249
10.0.26200.9168 — https://support.microsoft.com/help/5121003
10.0.26200.9106 — https://support.microsoft.com/help/5120994
10.0.28000.2704 — https://support.microsoft.com/help/5121000

Vulnerabilities 1

High 7.8

CVE-2026-66804 Public exploit

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.

Microsoft Windows 10 Version 22H2 Windows 11 Version 24H2 Windows 11 Version 25H2 Windows

Aug 11, 2026

Revision history

2026-10-07 #8
Updated an acknowledgement. This is an informational change only.
2026-09-30 #7
Updated an acknowledgement. This is an informational change only.
2026-08-27 #6
Updated an acknowledgement. This is an informational change only.
2026-08-18 #5
Acknowledgement Updated
2026-08-14 #4
Acknowledgement Updated
2026-08-13 #3
Acknowledgement Updated
2026-08-12 #2
Updated an acknowledgement. This is an informational change only.
2026-08-11 #1
Information published.

References

CVE-2026-66804 Microsoft Windows Cross Device Service Elevation of Privilege Vulnerability - HTML
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-66804
Microsoft Exploitability Index
https://www.microsoft.com/en-us/msrc/exploitability-index?rtc=1
Microsoft Support Lifecycle
https://support.microsoft.com/lifecycle
Common Vulnerability Scoring System
https://www.first.org/cvss