---
id: CVE-2021-33779
title: Windows AD FS Security Feature Bypass Vulnerability
summary: Windows AD FS Security Feature Bypass Vulnerability
severity: high
cvss: 8.1
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N'
vendor: microsoft
product: windows_server_2016
affected:
  - windows_server_2016
  - windows_server_2016 = 20h2
  - windows_server_2016 = 2004
  - windows_server_2019
published: '2021-07-14'
updated: '2026-08-10'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2021-33779'
references:
  - url: 'https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-33779'
    label: secure@microsoft.com
  - url: >-
      https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-33779
    label: af854a3a-2127-422b-91ae-364da2661108
tags:
  - nvd
epss: 0.0239
epssPercentile: 0.8324
ingestedAt: '2026-08-10T16:41:15.797Z'
---

## Overview

Windows AD FS Security Feature Bypass Vulnerability

## Affected

- `windows_server_2016`
- `windows_server_2016 = 20h2`
- `windows_server_2016 = 2004`
- `windows_server_2019`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.