Win32k Elevation of Privilege Vulnerability

cisa required action Apply updates per vendor instructions.

1. 2021-10-12 0-day patched (Project Zero)
2. 2021-10-12 First public exploit (Metasploit exploit/windows/local/cve_2021_40449)
3. 2021-10-13 Published
4. 2021-11-17 Added to CISA KEV
5. 2021-12-01 CISA patch deadline
6. 2025-02-07 CISA SSVC: exploitation active

Added

4 y ago (2021-11-17)

Patch by

2021-12-01 (4 y ago)

Ransomware

Known to be used in ransomware campaigns

Required action

Apply updates per vendor instructions.

Vendor, product

Microsoft, Windows

CISA name

Microsoft Windows Win32k Privilege Escalation Vulnerability

Detected in real attacks while still unknown to the vendor and the public, per Google Project Zero's 0day In-the-Wild tracker.

Patched

2021-10-12

Details

project zero tracker

How it is exploited and what it leads to, in MITRE ATT&CK terms.

• T1566 Phishing exploitation
• T1068 Exploitation for Privilege Escalation primary impact
• T1016 System Network Configuration Discovery secondary impact
• T1027 Obfuscated Files or Information secondary impact
• T1059.003 Windows Command Shell secondary impact
• T1071.001 Web Protocols secondary impact
• T1082 System Information Discovery secondary impact
• T1573.001 Symmetric Cryptography secondary impact

kev release 2025-07-28, att&ck v16.1. KEV to ATT&CK mappings by the MITRE Center for Threat-Informed Defense (Mappings Explorer, Apache-2.0). © 2026 The MITRE Corporation. This work is reproduced and distributed with the permission of The MITRE Corporation. Terms of use

Exploitation

Active, exploited in the wild

Automatable

no

Technical impact

total

Assessed

21 mo ago (2025-02-07)

81.94% chance of exploitation in the next 30 days, higher than 99.6% of all scored CVEs (FIRST EPSS, 2026-11-08).

• Metasploit exploit/windows/local/cve_2021_40449 Win32k NtGdiResetDC Use After Free Local Privilege Elevation metasploit exploit, good rank, 2021-10-12
• packetstormsecurity.com http://packetstormsecurity.com/files/164926/Win32k-NtGdiResetDC-Use-After-Free-Local-Privilege-Escalation.html referenced PoC, tagged "exploit" by a source, unverified

• Microsoft Windows 10 Version 1809
• Microsoft Windows Server 2019
• Microsoft Windows Server 2019 (Server Core installation)
• Microsoft Windows 10 Version 1909
• Microsoft Windows 10 Version 21H1
• Microsoft Windows Server 2022
• Microsoft Windows 10 Version 2004
• Microsoft Windows Server version 2004
• Microsoft Windows 10 Version 20H2
• Microsoft Windows Server version 20H2
• Microsoft Windows 11 version 21H2
• Microsoft Windows 10 Version 1507
• Microsoft Windows 10 Version 1607
• Microsoft Windows Server 2016
• Microsoft Windows Server 2016 (Server Core installation)
• Microsoft Windows 7
• Microsoft Windows 7 Service Pack 1
• Microsoft Windows 8.1
• Microsoft Windows Server 2008 Service Pack 2
• Microsoft Windows Server 2008 Service Pack 2 (Server Core installation)
• Microsoft Windows Server 2008 Service Pack 2
• Microsoft Windows Server 2008 R2 Service Pack 1
• Microsoft Windows Server 2008 R2 Service Pack 1 (Server Core installation)
• Microsoft Windows Server 2012
• Microsoft Windows Server 2012 (Server Core installation)
• Microsoft Windows Server 2012 R2
• Microsoft Windows Server 2012 R2 (Server Core installation)

Weakness

• CWE-416 Use After Free

• portal.msrc.microsoft.com /en-US/security-guidance/advisory/CVE-2021-40449

  patch, vendor-advisory

• packetstormsecurity.com /files/164926/Win32k-NtGdiResetDC-Use-After-Free-Local-Privilege-Escalation.html

  exploit, third-party-advisory, vdb-entry

• cisa.gov /known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-40449

  government-resource, us-government-resource

• CVE List CVE-2021-40449
• NVD CVE-2021-40449

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.