# Windows 11 26H1 privilege escalation flaw patched

Published: 2026-09-15 · Severity: routine
Canonical: https://vorant.io/reports/a4e6ec15-dd89-5757-959c-634b615a8033/windows-11-26h1-privilege-escalation-flaw-patched

> ANSSI advisory covers a privilege escalation vulnerability in Windows 11 26H1 (ARM64/x64) fixed in build 10.0.28000.2956.

ANSSI (CERT-FR) published an advisory describing a privilege escalation vulnerability, tracked as CVE-2026-85921, affecting Microsoft Windows 11 Version 26H1 on both ARM64 and x64 architectures. Systems running versions prior to build 10.0.28000.2956 are vulnerable. Exploitation of this flaw would allow an attacker to elevate privileges on an affected system, which could lead to greater control over the compromised host depending on the attacker's initial access level.

The advisory does not indicate that this vulnerability is currently being exploited in the wild; it is a standard vendor patch notification relayed by the French national CERT. Microsoft has released a security update addressing the issue, referenced in their September 14, 2026 security bulletin. Defenders should apply the update to bring affected Windows 11 26H1 systems to build 10.0.28000.2956 or later, and prioritize patching on systems where local access by lower-privileged users or processes is a realistic threat vector.

No further technical details, indicators of compromise, or exploitation context were provided in the source advisory. Organizations running Windows 11 26H1 on ARM64 or x64 platforms should verify build versions and apply the Microsoft-supplied patch through standard update channels.

## Mentioned in this report

- Vulnerabilities: CVE-2026-85921

Source reporting: https://www.cert.ssi.gouv.fr/avis/CERTFR-2026-AVI-1174

---

This is the free public brief from Vorant Threat Intelligence. When citing, attribute "Vorant" and link https://vorant.io/reports/a4e6ec15-dd89-5757-959c-634b615a8033/windows-11-26h1-privilege-escalation-flaw-patched.
Full IOC sets, deployable detections, the entity graph, TAXII 2.1 feed and real-time alerts: https://vorant.io/signup