CVE-2026-66804: Improper access control in Windows Cross Device Service allows an authorized attacker to elevate privileges lo

Q: How do I fix CVE-2026-66804?

windows 10 22h2: upgrade to 10.0.19045.7663; windows 11 24h2: upgrade to 10.0.26100.9106; windows 11 25h2: upgrade to 10.0.26200.9106. Exact commands for each OS are on this page.

Q: Is CVE-2026-66804 being exploited?

CVE-2026-66804 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-66804 affect?

CVE-2026-66804 affects windows 10 22h2, windows 11 24h2, windows 11 25h2. Severity is high (CVSS 7.8). Improper access control in Windows Cross Device Service allows an authorized attacker to elevate privileges locally.

Q: How urgent is CVE-2026-66804?

Priority 38/100. High severity; On your watchlist

Routine

HIGH 7.8WATCHLISTUPGRADEUPGRADEUPGRADE

CVE-2026-66804 is a high-severity flaw (CVSS 7.8) affecting windows 10 22h2, windows 11 24h2, windows 11 25h2. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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

Why this priority

High severity
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	7.8 (High)
Attack vector	Local
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.3% (top 78%)
CISA exploited list	No
Weakness	CWE-284
Published	2026-08-11
Last modified	2026-08-14

Publisher (CNA): Microsoft Corporation · Vendor: microsoft

Last updated 2026-08-14 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-08-11 17:19 UTCPublished CVE record published
2026-08-14 18:06 UTCUpdated Record last modified

microsoft windows 10 22h2 UPGRADE

Affected: < 10.0.19045.7663

Fixed in: 10.0.19045.7663

Safe to downgrade to: no unaffected older release

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

microsoft windows 11 24h2 UPGRADE

Affected: < 10.0.26100.9106

Fixed in: 10.0.26100.9106

Safe to downgrade to: no unaffected older release

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

microsoft windows 11 25h2 UPGRADE

Affected: < 10.0.26200.9106

Fixed in: 10.0.26200.9106

Safe to downgrade to: no unaffected older release

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

microsoft windows 11 26h1 UPGRADE

Affected: < 10.0.28000.2704

Fixed in: 10.0.28000.2704

Safe to downgrade to: no unaffected older release

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Advisories and coverage

Research and news

Google Project Zero: Windows Exploitation Techniques: Dangling COM Object Registrations 2026-09-21

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-66804?

windows 10 22h2: upgrade to 10.0.19045.7663; windows 11 24h2: upgrade to 10.0.26100.9106; windows 11 25h2: upgrade to 10.0.26200.9106. Exact commands for each OS are on this page.

Is CVE-2026-66804 being exploited?

CVE-2026-66804 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-66804 affect?

CVE-2026-66804 affects windows 10 22h2, windows 11 24h2, windows 11 25h2. Severity is high (CVSS 7.8). Improper access control in Windows Cross Device Service allows an authorized attacker to elevate privileges locally.

How urgent is CVE-2026-66804?

Priority 38/100. High severity; On your watchlist

Software pages

Windows vulnerabilities

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References

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