---
id: CVE-2026-20872
title: >-
  External control of file name or path in Windows NTLM allows an unauthorized
  attacker to perform spoofing over a network.
summary: >-
  External control of file name or path in Windows NTLM allows an unauthorized
  attacker to perform spoofing over a network.
severity: medium
cvss: 6.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N'
cwe:
  - CWE-73
vendor: microsoft
product: windows_10_1607
affected:
  - windows_10_1607 < 10.0.14393.8783
  - windows_10_1809 < 10.0.17763.8276
  - windows_10_21h2 < 10.0.19044.6809
  - windows_10_22h2 < 10.0.19045.6809
  - windows_11_23h2 < 10.0.22631.6491
  - windows_11_24h2 < 10.0.26100.7623
  - windows_11_25h2 < 10.0.26200.7623
  - windows_server_2008
  - windows_server_2008 = r2
  - windows_server_2012
  - windows_server_2012 = r2
  - windows_server_2016 < 10.0.14393.8783
  - windows_server_2019 < 10.0.17763.8276
  - windows_server_2022 < 10.0.20348.4648
  - windows_server_2022_23h2 < 10.0.25398.2092
  - windows_server_2025 < 10.0.26100.32230
patched:
  - windows_10_1607 10.0.14393.8783
  - windows_10_1809 10.0.17763.8276
  - windows_10_21h2 10.0.19044.6809
  - windows_10_22h2 10.0.19045.6809
  - windows_11_23h2 10.0.22631.6491
  - windows_11_24h2 10.0.26100.7623
  - windows_11_25h2 10.0.26200.7623
  - windows_server_2016 10.0.14393.8783
  - windows_server_2019 10.0.17763.8276
  - windows_server_2022 10.0.20348.4648
  - windows_server_2022_23h2 10.0.25398.2092
  - windows_server_2025 10.0.26100.32230
published: '2026-01-13'
updated: '2026-07-30'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-20872'
references:
  - url: 'https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-20872'
    label: secure@microsoft.com
  - url: >-
      https://www.vicarius.io/vsociety/posts/cve-2026-20872-detection-script-spoofing-vulnerability-in-windows-ntlm
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: >-
      https://www.vicarius.io/vsociety/posts/cve-2026-20872-mitigation-script-spoofing-vulnerability-in-windows-ntlm
    label: af854a3a-2127-422b-91ae-364da2661108
tags:
  - nvd
epss: 0.20059
epssPercentile: 0.97331
ingestedAt: '2026-07-31T06:58:52.869Z'
---

## Overview

External control of file name or path in Windows NTLM allows an unauthorized attacker to perform spoofing over a network.

## Affected

- `windows_10_1607 < 10.0.14393.8783`
- `windows_10_1809 < 10.0.17763.8276`
- `windows_10_21h2 < 10.0.19044.6809`
- `windows_10_22h2 < 10.0.19045.6809`
- `windows_11_23h2 < 10.0.22631.6491`
- `windows_11_24h2 < 10.0.26100.7623`
- `windows_11_25h2 < 10.0.26200.7623`
- `windows_server_2008`
- `windows_server_2008 = r2`
- `windows_server_2012`
- `windows_server_2012 = r2`
- `windows_server_2016 < 10.0.14393.8783`
- `windows_server_2019 < 10.0.17763.8276`
- `windows_server_2022 < 10.0.20348.4648`
- `windows_server_2022_23h2 < 10.0.25398.2092`
- `windows_server_2025 < 10.0.26100.32230`

## Remediation

Upgrade past the affected range:

- `windows_10_1607 10.0.14393.8783`
- `windows_10_1809 10.0.17763.8276`
- `windows_10_21h2 10.0.19044.6809`
- `windows_10_22h2 10.0.19045.6809`
- `windows_11_23h2 10.0.22631.6491`
- `windows_11_24h2 10.0.26100.7623`
- `windows_11_25h2 10.0.26200.7623`
- `windows_server_2016 10.0.14393.8783`
- `windows_server_2019 10.0.17763.8276`
- `windows_server_2022 10.0.20348.4648`
- `windows_server_2022_23h2 10.0.25398.2092`
- `windows_server_2025 10.0.26100.32230`