High 7.8Known exploited (CISA KEV)Published Oct 12, 2021

CVE-2021-40449Win32k Elevation of Privilege Vulnerability

Updated under an hour ago (Oct 27, 2026, 11:00 AM ET)

Does this affect you?

It affects Microsoft Windows 10 Version 1809 and 21 other products. Add what you run to find out whether that includes you.

CISA lists it as known exploited since Nov 17, 2021; federal agencies had to remediate by Dec 1, 2021, and it is known to be used in ransomware. Treat that date as your deadline.

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Every CVE for Microsoft Windows 10 Version 1809

Exploited in the last 30 days

Win32k Elevation of Privilege Vulnerability

CVSS: 7.8 HIGH (v3.1, CNA)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
Weakness (CWE): CWE-416
Known exploited: Added to CISA KEV Nov 17, 2021; federal remediation due Dec 1, 2021; known ransomware useApply updates per vendor instructions.
EPSS (exploitation in the next 30 days): 81.94% (percentile 100)
Assigned by: microsoft
NVD analysis: Analyzed
Record last updated: Oct 21, 2025
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

Microsoft Windows 10 Version 1809 microsoft:windows_10_1809	from 10.0.0 before 10.0.17763.2237	CNA record
Microsoft Windows Server 2019 microsoft:windows_server_2019	from 10.0.0 before 10.0.17763.2237	CNA record
Microsoft Windows 10 Version 1909 microsoft:windows_10_1909	from 10.0.0 before 10.0.18363.1854	CNA record
Microsoft Windows 10 Version 21H1 microsoft:windows_10_21h1	from 10.0.0 before 10.0.19041.1288	CNA record
Microsoft Windows Server 2022 microsoft:windows_server_2022	from 10.0.0 before 10.0.20348.288	CNA record
Microsoft Windows Server version 2004 microsoft:windows_server_2004	from 10.0.0 before 10.0.19041.1288	CNA record
Microsoft Windows 10 Version 20H2 microsoft:windows_10_20h2	from 10.0.0 before 10.0.19041.1288	CNA record
Microsoft Windows Server version 20H2 microsoft:windows_server_20h2	from 10.0.0 before 10.0.19042.1288	CNA record
Microsoft Windows 11 version 21H2 microsoft:windows_11_21h2	from 10.0.0 before 10.0.22000.258	CNA record
Microsoft Windows 10 Version 1507 microsoft:windows_10_1507	from 10.0.0 before 10.0.10240.19086	CNA record
1–10 of 38

References

References

https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-40449	x-refsource-misc, patch, vendor-advisory
http://packetstormsecurity.com/files/164926/Win32k-NtGdiResetDC-Use-After-Free-Local-Privilege-Escalation.html	x-refsource-misc, exploit, third-party-advisory, vdb-entry
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-40449	us-government-resource

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.