---
id: "CVE-2026-121673"
page: "https://infrastack.ai/live/CVE-2026-121673"
kind: "vulnerability"
aliases: ["CVE-2026-121673"]
title: "Windows Filter Manager: use-after-free lets a local user gain higher privileges"
severity: "high"
cvss: 7.8
epss: null
exploited: false
status: "open"
category: "infrastructure"
products: [{"name": "Windows 10 1607 / Server 2016", "fixed": ["10.0.14393.9688"], "affected": "< 10.0.14393.9688", "ecosystem": "microsoft"}, {"name": "Windows 10 1809 / Server 2019", "fixed": ["10.0.17763.9487"], "affected": "< 10.0.17763.9487", "ecosystem": "microsoft"}, {"name": "Windows 10 21H2", "fixed": ["10.0.19044.7846"], "affected": "< 10.0.19044.7846", "ecosystem": "microsoft"}, {"name": "Windows 10 22H2", "fixed": ["10.0.19045.7846"], "affected": "< 10.0.19045.7846", "ecosystem": "microsoft"}, {"name": "Windows Server 2022", "fixed": ["10.0.20348.5870"], "affected": "< 10.0.20348.5870", "ecosystem": "microsoft"}, {"name": "Windows 11 23H2", "fixed": ["10.0.22631.7711"], "affected": "< 10.0.22631.7711", "ecosystem": "microsoft"}, {"name": "Windows 11 24H2", "fixed": ["10.0.26100.9974"], "affected": "< 10.0.26100.9974", "ecosystem": "microsoft"}, {"name": "Windows 11 25H2", "fixed": ["10.0.26200.9974"], "affected": "< 10.0.26200.9974", "ecosystem": "microsoft"}, {"name": "Windows 11 26H2", "fixed": ["10.0.26300.9974"], "affected": "< 10.0.26300.9974", "ecosystem": "microsoft"}, {"name": "Windows 11 26H1", "fixed": ["10.0.28000.3501"], "affected": "< 10.0.28000.3501", "ecosystem": "microsoft"}, {"name": "Windows Server 2025", "fixed": ["10.0.26100.33822"], "affected": "< 10.0.26100.33822", "ecosystem": "microsoft"}]
ecosystems: []
tags: ["filter-manager", "infrastructure", "local-privilege-escalation", "windows", "windows-10", "windows-11", "windows-server"]
not_affected_if: ["no-local-untrusted-users", "patched-november-2026"]
published_at: "2026-11-10T19:20:30+00:00"
first_seen_at: "2026-11-10T19:25:09+00:00"
updated_at: "2026-11-10T21:45:13+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-121673", "first_seen_at": "2026-11-10T19:25:09+00:00"}, {"source": "analyst", "url": "https://api.msrc.microsoft.com/sug/v2.0/en-US/vulnerability/CVE-2026-121673", "first_seen_at": "2026-11-10T21:45:13+00:00", "cites": ["https://api.msrc.microsoft.com/sug/v2.0/en-US/vulnerability/CVE-2026-121673", "https://cveawg.mitre.org/api/cve/CVE-2026-121673"]}]
exploit_sources: []
---

# Windows Filter Manager: use-after-free lets a local user gain higher privileges

Link for people: https://infrastack.ai/live/CVE-2026-121673 (this .md is for agents)

A memory-safety bug in the Windows Filter Manager driver lets a user who already has local access corrupt memory and elevate their privileges. An attacker who can run code on the machine can gain system-level rights.

_Summary, check and fix written by a model from the sources; labelled as such._

## Affected

- microsoft:Windows 10 1607 / Server 2016 affected < 10.0.14393.9688 fixed 10.0.14393.9688
- microsoft:Windows 10 1809 / Server 2019 affected < 10.0.17763.9487 fixed 10.0.17763.9487
- microsoft:Windows 10 21H2 affected < 10.0.19044.7846 fixed 10.0.19044.7846
- microsoft:Windows 10 22H2 affected < 10.0.19045.7846 fixed 10.0.19045.7846
- microsoft:Windows Server 2022 affected < 10.0.20348.5870 fixed 10.0.20348.5870
- microsoft:Windows 11 23H2 affected < 10.0.22631.7711 fixed 10.0.22631.7711
- microsoft:Windows 11 24H2 affected < 10.0.26100.9974 fixed 10.0.26100.9974
- microsoft:Windows 11 25H2 affected < 10.0.26200.9974 fixed 10.0.26200.9974
- microsoft:Windows 11 26H2 affected < 10.0.26300.9974 fixed 10.0.26300.9974
- microsoft:Windows 11 26H1 affected < 10.0.28000.3501 fixed 10.0.28000.3501
- microsoft:Windows Server 2025 affected < 10.0.26100.33822 fixed 10.0.26100.33822

## How to check

Run winver or [System.Environment]::OSVersion / systeminfo to read the full OS build (e.g. 10.0.26100.xxxx; the UBR is the last number). You are exposed if it is below the fixed build for your version: 1607/Server 2016 < 14393.9688; 1809/Server 2019 < 17763.9487; 21H2 < 19044.7846; 22H2 < 19045.7846; Server 2022 < 20348.5870; Win11 23H2 < 22631.7711; 24H2 < 26100.9974; 25H2 < 26200.9974; 26H2 < 26300.9974; 26H1 < 28000.3501; Server 2025 < 26100.33822. Look up the KB for your version in the MSRC Update Guide entry for CVE-2026-121673.

## Fix

Install the November 2026 Windows cumulative update that brings the OS build to at least: Win10 1607/Server 2016 10.0.14393.9688; Win10 1809/Server 2019 10.0.17763.9487; Win10 21H2 10.0.19044.7846; Win10 22H2 10.0.19045.7846; Server 2022 10.0.20348.5870; Win11 23H2 10.0.22631.7711; Win11 24H2 10.0.26100.9974; Win11 25H2 10.0.26200.9974; Win11 26H2 10.0.26300.9974; Win11 26H1 10.0.28000.3501; Server 2025 10.0.26100.33822.

## Timeline

- 2026-11-10T19:25:09+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-121673
- 2026-11-10T21:45:13+00:00 analyst https://api.msrc.microsoft.com/sug/v2.0/en-US/vulnerability/CVE-2026-121673 — Microsoft CNA CVE record and MSRC API read: affected/fixed builds listed; MSRC says exploited No, not publicly disclosed, Exploitation Less Likely. KB numbers not in either source (JS-only update guide page not rendered). X/social not searched (no sign of discussion; low-profile LPE).

## Documents

- [advisory] MSRC Update Guide: CVE-2026-121673 Windows Filter Manager Elevation of Privilege https://api.msrc.microsoft.com/sug/v2.0/en-US/vulnerability/CVE-2026-121673
- [fix] CVE record (Microsoft CNA): CVE-2026-121673 affected builds and fixed builds https://cveawg.mitre.org/api/cve/CVE-2026-121673

## From the sources

Use after free in Windows Filter Manager allows an authorized attacker to elevate privileges locally.

---

_Free to read, with fair use of about 60 pages a minute. For higher limits or API access: sales@infrastack.ai_