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Weekly Signal
Live intelligence Updated 19 Aug 2026 · 20:27 UTC

Microsoft · Windows, Windows 10 1507, Windows 10 1607 +17 more

CVE-2021-40449

Microsoft Windows Win32k Privilege Escalation Vulnerability

Recommended action

Validate affected assets and exposure now, then remediate on an accelerated schedule. Microsoft Security patch CVE-2021-40449

View response plan
CVSS7.8
EPSS74.1%
KEVYes
ExploitationConfirmed exploitation
RemediationExplicit patch identified ↓

Assessment

Why it matters

CISA lists this vulnerability as known to be exploited; exploitation is confirmed; EPSS is 74.1%; technical severity is CVSS 7.8.

Win32k Elevation of Privilege Vulnerability

Who should care

  • Teams operating Windows, Windows 10 1507, Windows 10 1607 +17 more
  • Vulnerability and exposure management teams
  • Security operations teams monitoring exploitation activity

Response plan

What I would do

  1. Confirm whether Windows, Windows 10 1507, Windows 10 1607 +17 more is present in the environment.
  2. Identify affected versions and establish whether vulnerable services are exposed or reachable.
  3. Microsoft Security patch CVE-2021-40449
  4. Review relevant security telemetry for evidence of attempted or successful exploitation.
  5. Document the remediation decision and track it to verified completion.

Treatment intelligence

Remediation intelligence

Not yet verified

Vendor sources are listed before government and third-party guidance. Confirm product applicability and change prerequisites before deployment.

Verification noteAutomated link verification has not completed for this guidance yet.

Patch

Required Action

Technical details

CVSS vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CWE
CWE-416
Affected versions
Microsoft Windows; Microsoft Windows 10 1507 (End Excluding 10.0.10240.19086); Microsoft Windows 10 1607 (End Excluding 10.0.14393.4704); Microsoft Windows 10 1809 (End Excluding 10.0.17763.2237); Microsoft Windows 10 1909 (End Excluding 10.0.18363.1854); Microsoft Windows 10 2004 (End Excluding 10.0.19041.1288); Microsoft Windows 10 20h2 (End Excluding 10.0.19041.1288); Microsoft Windows 10 21h1 (End Excluding 10.0.19041.1288)
Fixed versions
Microsoft Windows 10 1507 (Fixed from 10.0.10240.19086); Microsoft Windows 10 1607 (Fixed from 10.0.14393.4704); Microsoft Windows 10 1809 (Fixed from 10.0.17763.2237); Microsoft Windows 10 1909 (Fixed from 10.0.18363.1854); Microsoft Windows 10 2004 (Fixed from 10.0.19041.1288); Microsoft Windows 10 20h2 (Fixed from 10.0.19041.1288); Microsoft Windows 10 21h1 (Fixed from 10.0.19041.1288); Microsoft Windows 11 21h2 (Fixed from 10.0.22000.258)
Published
12 October 2021
Attack vector
Local
Privileges required
Low
User interaction
None

Signal timeline

  1. CVE published
  2. Added to CISA KEV
  3. Latest EPSS score: 74.1%
  4. Signal calculated at 83

External references

Live public intelligence This assessment combines public-source evidence. Validate the affected product, version and exposure against your own environment before making a risk decision.