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Vulnerability Intelligence

CVE-2021-40449

HighExploitedPublic exploit

Win32k Elevation of Privilege Vulnerability

Published Oct 13, 2021 · Updated Oct 21, 2025

Key Facts

Patch immediately
  • CVE-2021-40449 is a high-severity vulnerability (CVSS 7.8 v3.1) affecting Windows 10 1507 (Microsoft), Windows 10 1607 (Microsoft), Windows 10 1809 (Microsoft) and 19 more products.
  • It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since Oct 12, 2021 and is known to be used in ransomware campaigns. Public exploit code is available.
  • EPSS estimates a 74% probability of exploitation in the next 30 days.
  • Fixed versions are available, including Windows 10 1507 10.0.10240.19086, Windows 10 1607 10.0.14393.4704, Windows 10 1809 10.0.17763.2237.
  • Brandefense priority: patch immediately, because it is listed as exploited in the wild.

CVSS v3.1

7.8

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

EPSS (30-day exploit likelihood)

74%

Higher than 99.4% of all scored CVEs

Exploited in the wild

Yes

4 catalog listings, used by ransomware

Public exploit code

Available

Proof-of-concept or weaponized module

Get the full CVE-2021-40449 brief as a PDF

Every affected product and fixed release, exploitation status and a first 24 hours response checklist, emailed within minutes.

Description

Win32k Elevation of Privilege Vulnerability

Known-Exploited Catalog Listings

CatalogAddedRemediation dueRansomware use
CISA KEVNov 17, 2021Dec 1, 2021Known
Industry KEV feedOct 12, 2021Dec 1, 2021Known
CIRCL KEVNov 17, 2021Dec 1, 2021Known
ENISA EUVDNov 17, 2021n/aNot reported

Required action: Apply updates per vendor instructions.

Affected Products

54 affected entries in total
ProductAffected versionsFixed in
Windows 10 1507Microsoft10.0.10240.1908610.0.10240.19086
Windows 10 1607Microsoft10.0.14393.470410.0.14393.4704
Windows 10 1809Microsoft10.0.17763.2237, 10.0.18363.1854, 10.0.19041.128810.0.17763.2237
Windows 10 1909Microsoft10.0.18363.185410.0.18363.1854
Windows 10 2004MicrosoftSee advisory10.0.19041.1288
17 more affected products in the full CVE brief

Patched Releases

Windows 10 1507

10.0.10240.19086

Windows 10 1607

10.0.14393.4704

Windows 10 1809

10.0.17763.2237, 10.0.18363.1854, 10.0.19041.1288

Windows 10 1909

10.0.18363.1854

Windows 10 2004

10.0.19041.1288

windows 10 20H2

10.0.19041.1288

windows 10 21H1

10.0.19041.1288

windows 11 21H2

10.0.22000.258

Windows 7

6.1.7601.25740

Windows 8.1

6.3.9600.20144

Windows Rt 8.1

6.3.9600.20144

Windows Server 2004

10.0.19041.1288

windows server 2008 R2

6.1.7601.25740

Windows Server 2008 Sp2

6.0.6003.21251

Windows Server 2012

6.2.9200.23490

windows server 2012 R2

6.3.9600.20144

Windows Server 2016

10.0.14393.4704

Windows Server 2019

10.0.17763.2237

Windows Server 2022

10.0.20348.288

windows server 20H2

10.0.19042.1288

Timeline

  1. Added to Industry KEV feed

    Oct 12, 2021

  2. Publicly disclosed

    Oct 13, 2021

  3. Added to CISA KEV

    Nov 17, 2021

  4. Added to CIRCL KEV

    Nov 17, 2021

  5. Added to ENISA EUVD

    Nov 17, 2021

  6. Last updated

    Oct 21, 2025

Weakness Type

  • CWE-416 Use After Free

References

14 more references in the full CVE brief

FAQ

Common Questions.

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