---
id: "CVE-2021-42287"
kind: "vulnerability"
aliases: ["CVE-2021-42287"]
title: "Microsoft Active Directory: Microsoft Active Directory Domain Services Privilege Escalation Vulnerability"
severity: "high"
cvss: 8.8
epss: 0.7717
exploited: true
status: "open"
category: "infrastructure"
products: [{"name": "Microsoft Active Directory", "fixed": [], "affected": "", "ecosystem": "vendor"}]
ecosystems: ["vendor"]
tags: ["active-directory", "domain-controllers", "exploited", "infrastructure", "ransomware", "windows-server"]
not_affected_if: ["no-domain-controllers"]
published_at: "2021-11-10T01:19:46+00:00"
first_seen_at: "2026-10-23T19:11:52+00:00"
updated_at: "2026-10-23T21:57:35+00:00"
sources: [{"source": "kev", "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2021-42287", "first_seen_at": "2026-10-23T19:11:52+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2021-42287", "first_seen_at": "2026-10-23T19:13:44+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2021-42287", "first_seen_at": "2026-10-23T21:57:35+00:00"}]
---

# Microsoft Active Directory: Microsoft Active Directory Domain Services Privilege Escalation Vulnerability

Microsoft Active Directory Domain Services has a privilege escalation flaw that lets an authenticated domain user gain higher privileges. CISA lists it as known exploited, and the sources say it is used in ransomware campaigns.

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

## Affected

- vendor:Microsoft Active Directory affected ? fixed ?

## Fix

Apply the Microsoft updates for the vendor advisory for CVE-2021-42287 on all domain controllers, per CISA required action: apply updates per vendor instructions.

## Timeline

- 2026-10-23T19:11:52+00:00 kev https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2021-42287
- 2026-10-23T19:13:44+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2021-42287
- 2026-10-23T21:57:35+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2021-42287

## From the sources

Microsoft Active Directory Domain Services contains an unspecified vulnerability that allows for privilege escalation.

CISA required action: Apply updates per vendor instructions.

---

_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_