# CVE-2026-85921 — Microsoft Windows 11 version 26H1

> As of 2026-09-17, CVE-2026-85921 is a HIGH-severity vulnerability in Microsoft Windows 11 version 26H1, CVSS v3.1 8.2, EPSS 0.2% (18.0th percentile). Threadlinqs Intelligence links 1 tracked threat campaign to CVE-2026-85921, most recently “Microsoft September 2026 Cloud Disclosure: 18 Elevation-of-Privilege, Information-Disclosure, and Spoofing Flaws Across Azure and Copilot AI Products, Plus a Windows Secure Kernel EoP (CVE-2026-85921)”.

**Last updated:** 2026-09-17

## What is CVE-2026-85921?

Double free in Windows Secure Kernel Mode allows an authorized attacker to elevate privileges locally.

The record classifies CVE-2026-85921 under weakness class [CWE-415](https://cwe.mitre.org/data/definitions/415.html). Its CVSS v3 base vector states that the flaw requires local access to the host, needs high-privilege credentials, needs no user interaction, and has high impact on confidentiality, integrity, availability. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 6 days ago.

## Severity and exploitation probability

- **CVSS v3.1 base score:** 8.2 — HIGH (`CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/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 18.0% of all scored CVEs
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 4.8/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- **Published:** 2026-09-14, last modified 2026-09-17

## Is CVE-2026-85921 being exploited?

No public exploitation evidence for CVE-2026-85921 is recorded in the sources Threadlinqs tracks — CISA KEV, Exploit-DB, public proof-of-concept repositories and ProjectDiscovery Nuclei — as of 2026-09-17. That is an absence of evidence in those feeds, not a guarantee that the vulnerability is unexploited.

## Affected products and versions

- **Microsoft**: Windows 11 version 26H1

## How to fix CVE-2026-85921

No vendor patch reference has been recorded for CVE-2026-85921 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.

## Threat activity tracking CVE-2026-85921

1 tracked threat in the Threadlinqs corpus references CVE-2026-85921, either in the campaign’s CVE list or as an indicator on the campaign record.

- [Microsoft September 2026 Cloud Disclosure: 18 Elevation-of-Privilege, Information-Disclosure, and Spoofing Flaws Across Azure and Copilot AI Products, Plus a Windows Secure Kernel EoP (CVE-2026-85921)](https://intel.threadlinqs.com/threat/TL-2026-2563) — CRITICAL · 2026-09-18

## Sources

Enriched from CVE.org, NVD, FIRST EPSS, GitHub Security Advisories. Last verified by Threadlinqs on 2026-09-18. 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-2026-85921)

Canonical: https://intel.threadlinqs.com/cve/CVE-2026-85921
Full detection coverage and IOCs for threats exploiting CVE-2026-85921 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp