# CVE-2026-66804 — Microsoft Windows 10 Version 22H2

> As of 2026-10-21, CVE-2026-66804 is a HIGH-severity vulnerability in Microsoft Windows 10 Version 22H2, CVSS v3.1 7.8, EPSS 0.2% (22.6th percentile). No Threadlinqs-tracked threat campaign has been attributed to CVE-2026-66804 as of 2026-10-21; the identifier is re-checked against the Threadlinqs threat corpus on every daily ingest.

**Last updated:** 2026-10-21

## What is CVE-2026-66804?

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

The record classifies CVE-2026-66804 under weakness class [CWE-284](https://intel.threadlinqs.com/cwe/CWE-284). Its CVSS v3 base vector states that the flaw requires local access to the host, needs low-privilege credentials, needs no user interaction, and has high impact on confidentiality, integrity, availability. 4 affected-product entries are recorded, across 1 vendor, listed below. The identifier was first published 90 days ago.

## Severity and exploitation probability

- **CVSS v3.1 base score:** 7.8 — HIGH (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C`)
- **EPSS (FIRST):** 0.2% probability of exploitation in the next 30 days, higher than 22.6% of all scored CVEs
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 6.8/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- **Published:** 2026-08-11

## Is CVE-2026-66804 being exploited?

Weaponised exploit code for CVE-2026-66804 is publicly available. 3 public proof-of-concept repositories are tracked for this identifier. It currently carries a trending score of 26 in the Threadlinqs vulnerability feed.

- [Rat5ak/CVE-2026-66804-CrossDevice-Service-EoP](https://github.com/Rat5ak/CVE-2026-66804-CrossDevice-Service-EoP) (github)
- [DavidCarliez/CVE-2026-66804-CrossDevice-LPE](https://github.com/DavidCarliez/CVE-2026-66804-CrossDevice-LPE) (github)
- [CypherHippie/CVE-2026-66804](https://github.com/CypherHippie/CVE-2026-66804) (github)

## Affected products and versions

- [Microsoft](https://intel.threadlinqs.com/vendors/microsoft): Windows 10 Version 22H2, Windows 11 Version 24H2, Windows 11 Version 25H2, Windows 11 version 26H1

## How to fix CVE-2026-66804

The record marks a vendor fix as available for CVE-2026-66804. Patch reference: [https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-66804](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-66804). Apply the vendor fix referenced above to every affected product listed in this record, then confirm the running version against the vendor advisory.

## Threat activity tracking CVE-2026-66804

No threat campaign in the Threadlinqs corpus currently references CVE-2026-66804, in its CVE list or as an indicator. The linkage is recomputed from the live corpus on every daily ingest, so this section fills in as soon as a tracked campaign cites the identifier.

## Sources

Enriched from CVE.org, NVD, FIRST EPSS, GitHub Security Advisories, public proof-of-concept repositories. This product uses the NVD API but is not endorsed or certified by the NVD.

**Vendor advisory and patch**

- [msrc.microsoft.com — vendor advisory](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-66804)

Canonical: https://intel.threadlinqs.com/cve/CVE-2026-66804
No Threadlinqs detection currently covers CVE-2026-66804; it is re-checked on every ingest.
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