What is CVE-2021-40449?

CVE-2021-40449 is Win32k Elevation of Privilege Vulnerability affecting Microsoft Windows 10 Version 1809, Windows Server 2019, Windows Server 2019 (Server Core installation), Windows 10 Version 1909, Windows 10 Version 21H1, Windows Server 2022, Windows 10 Version 2004, Windows Server version 2004, Windows 10 Version 20H2, Windows Server version 20H2, Windows 11 version 21H2, Windows 10 Version 1507, Windows 10 Version 1607, Windows Server 2016, Windows Server....

CVE-2021-40449 affects Microsoft Windows 10 Version 1809, Windows Server 2019, Windows Server 2019 (Server Core installation), Windows 10 Version 1909, Windows 10 Version 21H1, Windows Server 2022, Windows 10 Version 2004, Windows Server version 2004, Windows 10 Version 20H2, Windows Server version 20H2, Windows 11 version 21H2, Windows 10 Version 1507, Windows 10 Version 1607, Windows Server 2016, Windows Server.... Previdian lists 27 version rows; examples include 10.0.0 to < 10.0.17763.2237.

Vulnerability report

Trusted Third Party Report Confirmed Confidence In CISA KEV

CVE-2021-40449

Q: Have exploitation attempts been observed?

Yes. Exploitation attempts have been reported for this vulnerability. Previdian lists it as a known exploited vulnerability. Listed in CISA KEV. Confidence is confirmed.

Q: What should we do?

Prioritize remediation. Validate affected assets and apply vendor fixes on an accelerated timeline.

Win32k Elevation of Privilege Vulnerability

Microsoft / Windows 10 Version 1809 · affected before 10.0.17763.2237

Watch CVE-2021-40449 Browse KEV feed

Severity: CVSS 7.8 · High
Confidence: Confirmed
Exploit status: Trusted Third Party Report
EPSS: 81.9%
First observed: —
Last observed: —

Decision summary

What security teams need to know first

Direct answers before the deeper technical record.

What it is

CVE-2021-40449 is Win32k Elevation of Privilege Vulnerability affecting Microsoft Windows 10 Version 1809 and 26 other products.

Have exploitation attempts been observed?

Yes. Exploitation attempts have been reported for this vulnerability. Previdian lists it as a known exploited vulnerability. Listed in CISA KEV. Confidence is confirmed.

Who is affected?

Affected products include Microsoft / Windows 10 Version 1809 and 26 other products, including affected before 10.0.17763.2237, affected before 10.0.18363.1854, and affected before 10.0.19041.1288.

What should we do?

Prioritize remediation. Validate affected assets and apply vendor fixes on an accelerated timeline.

Overview

Win32k Elevation of Privilege Vulnerability

Vendor Product Affected Status

Microsoft Affected

Windows 10 Version 1809

Before 10.0.17763.2237

Affected

Microsoft Affected

Windows Server 2019

Before 10.0.17763.2237

Affected

Microsoft Affected

Windows Server 2019 (Server Core installation)

Before 10.0.17763.2237

Affected

Microsoft Affected

Windows 10 Version 1909

Before 10.0.18363.1854

Affected

Microsoft Affected

Windows 10 Version 21H1

Before 10.0.19041.1288

Affected

Microsoft Affected

Windows Server 2022

Before 10.0.20348.288

Affected

Microsoft Affected

Windows 10 Version 2004

Before 10.0.19041.1288

Affected

Microsoft Affected

Windows Server version 2004

Before 10.0.19041.1288

Affected

Microsoft Affected

Windows 10 Version 20H2

Before 10.0.19041.1288

Affected

Microsoft Affected

Windows Server version 20H2

Before 10.0.19042.1288

Affected

Microsoft Affected

Windows 11 version 21H2

Before 10.0.22000.258

Affected

Microsoft Affected

Windows 10 Version 1507

Before 10.0.10240.19086

Affected

Microsoft Affected

Windows 10 Version 1607

Before 10.0.14393.4704

Affected

Microsoft Affected

Windows Server 2016

Before 10.0.14393.4704

Affected

Microsoft Affected

Windows Server 2016 (Server Core installation)

Before 10.0.14393.4704

Affected

Microsoft Affected

Windows 7

Before 6.1.7601.25740

Affected

Microsoft Affected

Windows 7 Service Pack 1

Before 6.1.7601.25740

Affected

Microsoft Affected

Windows 8.1

Before 6.3.9600.20144

Affected

Microsoft Affected

Windows Server 2008 Service Pack 2

Before 6.0.6003.21251

Affected

Microsoft Affected

Windows Server 2008 Service Pack 2 (Server Core installation)

Before 6.0.6003.21251

Affected

Microsoft Affected

Windows Server 2008 Service Pack 2

Before 6.0.6003.21251

Affected

Microsoft Affected

Windows Server 2008 R2 Service Pack 1

Before 6.1.7601.25740

Affected

Microsoft Affected

Windows Server 2008 R2 Service Pack 1 (Server Core installation)

Before 6.1.7601.25740

Affected

Microsoft Affected

Windows Server 2012

Before 6.2.9200.23490

Affected

Microsoft Affected

Windows Server 2012 (Server Core installation)

Before 6.2.9200.23490

Affected

Microsoft Affected

Windows Server 2012 R2

Before 6.3.9600.20144

Affected

Microsoft Affected

Windows Server 2012 R2 (Server Core installation)

Before 6.3.9600.20144

Affected

Published: 13 Oct 2021
Exploitation Attempts Reported: 17 Nov 2021
Attack vector: Local
Complexity: Low
Privileges: Low
User interaction: None

CVE References

CVE Record CVE.org · CVE Record https://www.cve.org/CVERecord?id=CVE-2021-40449
portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-40449 portal.msrc.microsoft.com · CVE Record https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CV...
packetstormsecurity.com/files/164926/Win32k-NtGdiResetDC-Use-After-F... packetstormsecurity.com · CVE Record http://packetstormsecurity.com/files/164926/Win32k-NtGdiResetDC-Use-A...

Exploitation evidence

Evidence of exploitation attempts

Third-party attestation and first-party sensor observation are shown separately so teams can judge the evidence chain.

Exploitation Attempts Observed in the Wild

CISA

Recorded 17 Nov 2021

A trusted third party reported exploitation attempts.

Targeted by Malware-Related Exploitation Attempts

CISA

Recorded 17 Nov 2021

Exploitation attempts against this vulnerability are associated with malware-related payloads.

Proof of concept available

GitHub

Recorded 20 Oct 2021

Public scanner or PoC coverage increases practical exploitability.

Known exploited vulnerability sources

Per-source evidence links for KEV attestations are available through the Previdian Pro API.

Learn about Pro API access

Source	Added
CISA First	2021-11-17 00:00 UTC

Detection

Operational artifacts and observed signals

Make the evidence actionable in scanner, SOC, and edge-control workflows.

Scanner coverage

Metasploit template detected 28 Apr 2025.

View Metasploit template

Virtual patch status

No Previdian virtual patch is currently available. Future rules ship for ModSecurity, Cloudflare, and AWS WAF.

Learn about virtual patches →

Scanner Artifacts

Scanner and exploit-framework references linked to this CVE.

Scanner	Reference	Detected
Metasploit	https://github.com/rapid7/metasploit-framework/blob/master/modules/exploits/windows/local/cve_2021_40449.rb	28 Apr 2025

Risk and context

Severity, weaknesses, and research context

CVSS v3.1

7.8 High

Potential damage if exploited. Separate from whether attackers are using it.

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C

EPSS

81.9%

Estimated chance of exploitation in the next 30 days. Previdian's warning comes from evidence, not this score.

Weaknesses

Use After Free CWE-416

Potential Proof of Concepts

These PoCs are unverified and could contain malware. Use at your own risk.

Kristal-g/CVE-2021-40449_poc

github · Created 2021-11-07 16:15:19 UTC · 52 stars · AI assessment 90%

Exploit for CVE-2021-40449

hakivvi/CVE-2021-40449

github · Created 2021-10-25 04:58:49 UTC · 41 stars · AI assessment 90%

LPE exploit for a UAF in Windows (CVE-2021-40449).

KaLendsi/CVE-2021-40449-Exploit

github · Created 2021-10-20 09:24:36 UTC · 96 stars · AI assessment 90%

windows 10 14393 LPE

cve_2021_40449

metasploit · Created Unknown

Metasploit module for CVE-2021-40449

Timeline

From disclosure to observed exploitation attempts

28 Apr 2025
15:02 UTC

Metasploit module available

Exploit module available
17 Nov 2021
00:00 UTC

Added to CISA KEV

Listed in the CISA Known Exploited Vulnerabilities catalog
17 Nov 2021
00:00 UTC

Targeted by malware-related exploitation attempts

Malware-related exploitation attempts or payloads reported
20 Oct 2021
09:24 UTC

Public PoC available

Public proof-of-concept code published
13 Oct 2021
00:26 UTC

CVE published

Vulnerability disclosed publicly
02 Sep 2021
00:00 UTC

CVE ID reserved

Identifier reserved by the CNA

Pro API

Automate this intelligence

Confidence, exploit status, sensor telemetry, PoCs, scanner integrations, mentions, and tags are available programmatically for VM, SOC, and CTI workflows.

Start 14-day Pro trial Read API docs

Evidence confidence and provenance
First-party sensor telemetry
PoC and scanner references
Affected versions and enrichment
Automation-ready JSON delivery

GET /api/v2/pro/kevs/CVE-2021-40449

Sample API response

{
  "cve_id": "CVE-2021-40449",
  "confidence": "Confirmed",
  "cvss_score": 7.8,
  "cvss_estimated": false,
  "epss_score": 0.81936,
  "exploit_status": {
    "exploited_in_the_wild": true,
    "active_exploitation_observed": false
  },
  "sensor_telemetry": { "attempts": 0, "sensors": 0 }
}

CVE-2021-40449

Win32k Elevation of Privilege Vulnerability

Tags

CVE References

Exploitation Attempts Observed in the Wild

Targeted by Malware-Related Exploitation Attempts

Proof of concept available

Known exploited vulnerability sources

Scanner coverage

Virtual patch status

Scanner Artifacts

Weaknesses

Potential Proof of Concepts

Metasploit module available

Added to CISA KEV

Targeted by malware-related exploitation attempts

Public PoC available

CVE published

CVE ID reserved

Automate this intelligence