CVE-2021-43226

mediumpriority · act · 90OT risk · criticalKEV · exploitedEPSS 0.033 · 88 %ileexploit · PoCDEEURUUS

grimoire priorityP0 · Act now

Exploitable?

Yes · in the wild

CISA KEV · 1 exploit · PoC

Likely / severe?

3.28% (88th) EPSS

CVSS 4.6 · medium

Is it mine?

101 products

Check your exposure

Who says so?

4 sources

cnnvd · enisa_euvd · fstec_bdu · cert_bund

added 2025-10-06remediate by 2025-10-27

required action Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

EPSS · scored 2026-10-27

Microsoft Windows Privilege Escalation Vulnerability

Windows Common Log File System Driver Elevation of Privilege Vulnerability

cvss

Technical severity, 0–10. One row per scoring source.

7.8

010

base score 0–10 · higher = more severe · hover a vector to decode⚠ sources disagree · medium–high · 4.6–7.8

v2.04.6mediumAV:L/AC:L/Au:N/C:P/I:P/A:Pprimary · NVD / NIST USexploitability 3.9 · impact 6.4

v3.17.8highCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Hprimary · NVD / NIST USexploitability 1.8 · impact 5.9

v3.17.8highAV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Hsecondary · FSTEC (BDU) RU

v3.17.8highCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:Csecondary · ENISA EU

v3.17.8highCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Hsecondary · secure@microsoft.com USexploitability 1.8 · impact 5.9

v3.17.8highCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:Hsecondary · CVSS-BT (t0sche)

ssvc

A stakeholder decision — act, attend, or track — from exploitation and impact.

Exploitation: active · Automatable: no · Technical Impact: totalcoordinatorcisa_ssvcUS

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-269US

exploits (1)

Public proof-of-concept and weaponised exploit code.

Rosayxy/cve-2021-43226PoCa Proof of Concept of cve-2021-43226,stack overflow in Windows driver clfs.sysPoC · poc_in_github

affected products (101)

Products and version ranges known to be affected.

Hitachi Storageall versionscert_bundDEcpe:/h:hitachi:storage:-
Microsoft Windows 10all versionscert_bundDEcpe:/o:microsoft:windows_10:-
Microsoft Windows 10 Version 1607all versionscert_bundDEcpe:/o:microsoft:windows_10:version_1607
Microsoft Windows 10 Version 1809all versionscert_bundDEcpe:/o:microsoft:windows_10:version_1809
Microsoft Windows 10 Version 1909all versionscert_bundDEcpe:/o:microsoft:windows_10:version_1909
Microsoft Windows 10 Version 2004all versionscert_bundDEcpe:/o:microsoft:windows_10:version_2004
Microsoft Windows 10 Version 20H2all versionscert_bundDEcpe:/o:microsoft:windows_10:version_20h2
Microsoft Windows 10 Version 21H1all versionscert_bundDEcpe:/o:microsoft:windows_10:version_21h1
Microsoft Windows 10 Version 21H2all versionscert_bundDEcpe:/o:microsoft:windows_10:version_21h2
Microsoft Windows 11all versionscert_bundDEcpe:/o:microsoft:windows_11:-
Microsoft Windows 7 SP1all versionscert_bundDEcpe:/o:microsoft:windows_7:sp1
Microsoft Windows 8.1all versionscert_bundDEcpe:/o:microsoft:windows_8.1:-
Microsoft Windows RT 8.1all versionscert_bundDEcpe:/o:microsoft:windows_rt_8.1:-
Microsoft Windows Server 2008 R2 SP1all versionscert_bundDEcpe:/o:microsoft:windows_server_2008_r2:sp_1
Microsoft Windows Server 2008 SP2all versionscert_bundDEcpe:/o:microsoft:windows_server_2008:sp2:x64
Microsoft Windows Server 2012all versionscert_bundDEcpe:/o:microsoft:windows_server_2012:::server_core_installation
Microsoft Windows Server 2012 R2all versionscert_bundDEcpe:/o:microsoft:windows_server_2012_r2:-
Microsoft Windows Server 2016all versionscert_bundDEcpe:/o:microsoft:windows_server_2016:server_2016:r2
Microsoft Windows Server 2019all versionscert_bundDEcpe:/o:microsoft:windows_server_2019:server_core_installation
Microsoft Windows Server 2022all versionscert_bundDEcpe:/o:microsoft:windows_server_2022:-

showing 20 of 101

advisories (1)

Vendor and ecosystem advisories describing this.

WID-SEC-W-2025-2220Microsoft Windows und Microsoft Windows Server: Mehrere SchwachstellenDeutsch2021-12-14csaf · cert_bundDE
Ein entfernter, anonymer, authentisierter oder lokaler Angreifer kann mehrere Schwachstellen in Microsoft Windows und Microsoft Windows Server ausnutzen, um einen Denial of Service Zustand zu verursachen, seine Privilegien zu erhöhen, vertrauliche Informationen offenzulegen und beliebigen Code auszuführen.

also known as (4)

Other names and identifiers for this entity.

sources

Which sources assert this record, and when.

cnnvd enisa_euvd fstec_bdu cert_bund NVD CVE.org MITRE

published 2021-12-15modified 2026-08-22

references (8)

External citations — patches, advisories, analysis.

scry

Attackers weaponise vulnerabilities like this against internet-exposed services. See what is exposed on your perimeter with a free passive scan.

Free scan