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. 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.
Affected products and versions
- 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. 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.