---
id: CVE-2026-83991
title: >-
  Missing authentication for critical function in Windows Cloud Files Mini
  Filter Driver allows an authorized attacker to perform tampering locally.
summary: >-
  Missing authentication for critical function in Windows Cloud Files Mini
  Filter Driver allows an authorized attacker to perform tampering locally.
severity: medium
cvss: 5.5
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N'
cwe:
  - CWE-306
vendor: microsoft
product: windows_10_1809
affected:
  - windows_10_1809 < 10.0.17763.9245
  - windows_10_21h2 < 10.0.19044.7725
  - windows_10_22h2 < 10.0.19045.7725
  - windows_11_23h2 < 10.0.22631.7582
  - windows_11_24h2 < 10.0.26100.9445
  - windows_11_25h2 < 10.0.26200.9445
  - windows_11_26h1 < 10.0.28000.2954
  - windows_server_2019 < 10.0.17763.9245
  - windows_server_2022 < 10.0.20348.5622
  - windows_server_2025 < 10.0.26100.33438
patched:
  - windows_10_1809 10.0.17763.9245
  - windows_10_21h2 10.0.19044.7725
  - windows_10_22h2 10.0.19045.7725
  - windows_11_23h2 10.0.22631.7582
  - windows_11_24h2 10.0.26100.9445
  - windows_11_25h2 10.0.26200.9445
  - windows_11_26h1 10.0.28000.2954
  - windows_server_2019 10.0.17763.9245
  - windows_server_2022 10.0.20348.5622
  - windows_server_2025 10.0.26100.33438
published: '2026-09-08'
updated: '2026-09-09'
sourceUpdated: '2026-09-09T20:14:54.747'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-83991'
references:
  - url: 'https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-83991'
    label: secure@microsoft.com
tags:
  - nvd
  - cve.org
  - exploit-available
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-09-09T18:34:37.479939Z'
epss: 0.00341
epssPercentile: 0.27611
exploits:
  github: 2
  githubRepos:
    - 'https://github.com/karollooool/CVE-2026-83991-writeup-and-poc'
    - 'https://github.com/ZeroDayVPN/CVE-2026-83991-WriteUP-and-PoC'
  checkedAt: '2026-09-21T15:30:56.503Z'
exploitAvailable: true
ingestedAt: '2026-09-08T19:08:49.633Z'
---

## Overview

Missing authentication for critical function in Windows Cloud Files Mini Filter Driver allows an authorized attacker to perform tampering locally.

## Affected

- `windows_10_1809 < 10.0.17763.9245`
- `windows_10_21h2 < 10.0.19044.7725`
- `windows_10_22h2 < 10.0.19045.7725`
- `windows_11_23h2 < 10.0.22631.7582`
- `windows_11_24h2 < 10.0.26100.9445`
- `windows_11_25h2 < 10.0.26200.9445`
- `windows_11_26h1 < 10.0.28000.2954`
- `windows_server_2019 < 10.0.17763.9245`
- `windows_server_2022 < 10.0.20348.5622`
- `windows_server_2025 < 10.0.26100.33438`

## Remediation

Upgrade past the affected range:

- `windows_10_1809 10.0.17763.9245`
- `windows_10_21h2 10.0.19044.7725`
- `windows_10_22h2 10.0.19045.7725`
- `windows_11_23h2 10.0.22631.7582`
- `windows_11_24h2 10.0.26100.9445`
- `windows_11_25h2 10.0.26200.9445`
- `windows_11_26h1 10.0.28000.2954`
- `windows_server_2019 10.0.17763.9245`
- `windows_server_2022 10.0.20348.5622`
- `windows_server_2025 10.0.26100.33438`