CVE-2021-43226 | Windows Common Log File System Driver Elevation of Privilege Vulnerability

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Windows Common Log File System Driver Elevation of Privilege Vulnerability

Published: 2021-12-15 Last update: 2026-06-17 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-43226 is rated Critical Active Threat (81.3/100): CVSS High severity, with medium exploitation likelihood (EPSS 3.07%). CISA KEV confirms active exploitation (added 2025-10-06) affecting Microsoft / Windows. Unauthenticated remote administrative access may be possible. The CISA remediation deadline has passed—treat as an emergency patch priority.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

CISA KEV Record for CVE-2021-43226

Name: Microsoft Windows Privilege Escalation Vulnerability · CISA KEV detail

Exploit added: 2025-10-06

Action due: 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.

Exploit prediction scoring system (EPSS) score for CVE-2021-43226

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 8.39% 3.07% -5.32%
2 2026-04-11 7.31% 8.39% +1.08%
3 2026-03-10 — 7.31% —

Full EPSS history (40 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-43226

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.8 3.1 HIGH
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:L)
They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 1.8 5.9 [email protected]
7.8 3.1 HIGH
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:L)
They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 1.8 5.9 [email protected]
4.6 2.0 MEDIUM
AV:L/AC:L/Au:N/C:P/I:P/A:P Click to expand
Access vector (AV:L)
Requires local access to the target system.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:P)
Partial confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:P)
Partial availability impact.
 3.9 6.4 [email protected]

Weakness enumeration for CVE-2021-43226

Affected software / configurations for CVE-2021-43226

Vendor Product Version Raw CPE
microsoft windows_10_1507 < 10.0.10240.19145 cpe:2.3:o:microsoft:windows_10_1507:*:*:*:*:*:*:x64:*
microsoft windows_10_1507 < 10.0.10240.19145 cpe:2.3:o:microsoft:windows_10_1507:*:*:*:*:*:*:x86:*
microsoft windows_10_1607 < 10.0.14393.4825 cpe:2.3:o:microsoft:windows_10_1607:*:*:*:*:*:*:x64:*
microsoft windows_10_1607 < 10.0.14393.4825 cpe:2.3:o:microsoft:windows_10_1607:*:*:*:*:*:*:x86:*
microsoft windows_10_1809 < 10.0.17763.2366 cpe:2.3:o:microsoft:windows_10_1809:*:*:*:*:*:*:*:*
microsoft windows_10_1909 < 10.0.18363.1977 cpe:2.3:o:microsoft:windows_10_1909:*:*:*:*:*:*:*:*
microsoft windows_10_2004 < 10.0.19041.1415 cpe:2.3:o:microsoft:windows_10_2004:*:*:*:*:*:*:*:*
microsoft windows_10_20h2 < 10.0.19042.1415 cpe:2.3:o:microsoft:windows_10_20h2:*:*:*:*:*:*:arm64:*
microsoft windows_10_20h2 < 10.0.19042.1415 cpe:2.3:o:microsoft:windows_10_20h2:*:*:*:*:*:*:x86:*
microsoft windows_10_21h1 < 10.0.19043.1415 cpe:2.3:o:microsoft:windows_10_21h1:*:*:*:*:*:*:*:*
microsoft windows_10_21h2 < 10.0.19044.1415 cpe:2.3:o:microsoft:windows_10_21h2:*:*:*:*:*:*:*:*
microsoft windows_11_21h2 < 10.0.22000.376 cpe:2.3:o:microsoft:windows_11_21h2:*:*:*:*:*:*:*:*
microsoft windows_7 — cpe:2.3:o:microsoft:windows_7:-:sp1:*:*:*:*:*:*
microsoft windows_8.1 — cpe:2.3:o:microsoft:windows_8.1:-:*:*:*:*:*:*:*
microsoft windows_rt_8.1 — cpe:2.3:o:microsoft:windows_rt_8.1:-:*:*:*:*:*:*:*
microsoft windows_server_2004 < 10.0.19041.1415 cpe:2.3:o:microsoft:windows_server_2004:*:*:*:*:*:*:*:*
microsoft windows_server_2008 — cpe:2.3:o:microsoft:windows_server_2008:-:sp2:*:*:*:*:x64:*
microsoft windows_server_2008 — cpe:2.3:o:microsoft:windows_server_2008:-:sp2:*:*:*:*:x86:*
microsoft windows_server_2008 r2 cpe:2.3:o:microsoft:windows_server_2008:r2:sp1:*:*:*:*:x64:*
microsoft windows_server_2012 — cpe:2.3:o:microsoft:windows_server_2012:-:*:*:*:*:*:*:*
microsoft windows_server_2012 r2 cpe:2.3:o:microsoft:windows_server_2012:r2:*:*:*:*:*:*:*
microsoft windows_server_2016 < 10.0.14393.4825 cpe:2.3:o:microsoft:windows_server_2016:*:*:*:*:*:*:*:*
microsoft windows_server_2019 < 10.0.17763.2366 cpe:2.3:o:microsoft:windows_server_2019:*:*:*:*:*:*:*:*
microsoft windows_server_2022 < 10.0.20348.405 cpe:2.3:o:microsoft:windows_server_2022:*:*:*:*:*:*:*:*
microsoft windows_server_20h2 < 10.0.19042.1415 cpe:2.3:o:microsoft:windows_server_20h2:*:*:*:*:*:*:*:*

References for CVE-2021-43226

cvelogic Threat Intelligence