Is CVE-2021-33771 actively exploited?

Yes. KEV Intelligence tracks CVE-2021-33771 as a known exploited vulnerability. Confidence is confirmed.

What exploitation activity has KEV Intelligence observed?

KEV Intelligence has not yet recorded sensor-observed exploitation attempts for CVE-2021-33771. Our sensors continue to monitor for activity targeting this CVE.

Which versions are affected?

CVE-2021-33771 affects Microsoft Windows 10 Version 1507 and 15 other products. KEV Intelligence lists 17 version rows; examples include 10.0.10240.0 to < 10.0.10240.19003, 10.0.14393.0 to < 10.0.14393.4530, and 10.0.17763.0 to < 10.0.17763.2061.

Yes. CVE-2021-33771 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.

CVE-2021-33771 Exploited in the Wild — Windows 10 Version 1507, Windows 10 Version 1607, Windows 10 Version 1809, Windows 10 Version 1909, Windows 10 Version 2004, Windows 10 Version 20H2, Windows 10 Version 21H1, Windows 8.1, Windows Server 2012 R2, Windows Server 2012 R2 (Server Core installation), Windows Server 2016, Windows Server 2016 (Server Core installation), Windows Server 2019, Windows Server 2019 (Server Core installation), Windows Server version 2004, Windows Server version 20H2

Q: What is CVE-2021-33771?

CVE-2021-33771 is Windows Kernel Elevation of Privilege Vulnerability affecting Microsoft Windows 10 Version 1507 and 15 other products.

Q: How should organizations remediate it?

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

Q: Is it in CISA KEV?

Yes. CVE-2021-33771 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.

Decision summary

What security teams need to know first

Direct answers before the deeper technical record.

What it is

CVE-2021-33771 is Windows Kernel Elevation of Privilege Vulnerability affecting Microsoft Windows 10 Version 1507 and 15 other products.

Is it exploited?

Yes. KEV Intelligence tracks this CVE as a known exploited vulnerability. Confidence is confirmed.

Who is affected?

Microsoft / Windows 10 Version 1507 affected before 10.0.10240.19003.

What should we do?

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

Overview

Windows Kernel Elevation of Privilege Vulnerability

Vendor Product Affected Status

Microsoft Windows 10 Version 1507 Before 10.0.10240.19003 Affected

Microsoft Windows 10 Version 1607 Before 10.0.14393.4530 Affected

Microsoft Windows 10 Version 1809 Before 10.0.17763.2061 Affected

Microsoft Windows 10 Version 1909 Before 10.0.18363.1679 Affected

Microsoft Windows 10 Version 2004 Before 10.0.19041.1110 Affected

Microsoft Windows 10 Version 20H2 Before 10.0.19042.1110 Affected

Microsoft Windows 10 Version 21H1 Before 10.0.19043.1110 Affected

Microsoft Windows 8.1 Before 6.3.9600.20069 Affected

Microsoft Windows Server 2012 R2 Before 6.3.9600.20069 Affected

Microsoft Windows Server 2012 R2 (Server Core installation) Before 6.3.9600.20069 Affected

Microsoft Windows Server 2016 Before 10.0.14393.4530 Affected

Microsoft Windows Server 2016 (Server Core installation) Before 10.0.14393.4530 Affected

Microsoft Windows Server 2019 Before 10.0.17763.2061 Affected

Microsoft Windows Server 2019 (Server Core installation) Before 10.0.17763.2061 Affected

Microsoft Windows Server version 2004 Before 10.0.19041.1110 Affected

Microsoft Windows Server version 20H2 Before 10.0.19042.1110 Affected

View vendor advisory

Published: 14 Jul 2021
Exploitation Reported: 03 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-2021-33771
Windows Kernel Elevation of Privilege Vulnerability msrc.microsoft.com · Vendor Advisory https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-33771

Exploitation evidence

Why KEV Intelligence marks this CVE as exploited

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

Exploited in the wild

CISA

Recorded 03 Nov 2021

Independent exploitation attestation added to the KEV Intelligence record.

Known exploited vulnerability sources

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

Learn about Pro API access

Source	Added
CISA First	2021-11-03 00:00 UTC
CVE	2026-08-10 15:31 UTC

Detection

Operational artifacts and observed signals

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

Observed signals

Request targets: 0
User-Agents: 0

Raw values available in Pro and Enterprise.

Scanner coverage

No scanner integrations recorded yet.

Virtual patch status

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

Learn about virtual patches →

No detection artifacts or sensor request patterns are available for this CVE yet.

Check back as sensor telemetry and scanner integrations are updated.

Risk and context

Severity, weaknesses, and research context

CVSS v3.1

7.8 High

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

EPSS

10.2%

All CVSS Scores

CVSS v3.1 7.8 High

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

CVSS v2.0 7.2 High

AV:L/AC:L/Au:N/C:C/I:C/A:C

Timeline

From disclosure to observed exploitation

10 Aug 2026
KEV confirmed by CVE

Exploitation attested by an external source
03 Nov 2021
Added to CISA KEV

Listed in the CISA Known Exploited Vulnerabilities catalog
14 Jul 2021
CVE published

Vulnerability disclosed publicly
28 May 2021
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.

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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-2021-33771

Free JSON includes basic KEV fields

{
  "cve_id": "CVE-2021-33771",
  "confidence": "Confirmed",
  "cvss_score": 7.8,
  "cvss_estimated": false,
  "epss_score": 0.10172,
  "exploit_status": {
    "exploited_in_the_wild": true,
    "active_exploitation_observed": false
  },
  "sensor_telemetry": { "attempts": 0, "sensors": 0 }
}

CVE-2021-33771