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Known Exploited Vulnerability
7.8
HIGH CVSS 3.1
CVE-2021-43226
Microsoft Windows Privilege Escalation Vulnerability - [Actively Exploited]
Description

Windows Common Log File System Driver Elevation of Privilege Vulnerability

INFO

Published Date :

Dec. 15, 2021, 3:15 p.m.

Last Modified :

Oct. 22, 2025, 12:17 a.m.

Remotely Exploit :

No

Source :

[email protected]
CISA Notification
CISA KEV (Known Exploited Vulnerabilities)

For the benefit of the cybersecurity community and network defenders—and to help every organization better manage vulnerabilities and keep pace with threat activity—CISA maintains the authoritative source of vulnerabilities that have been exploited in the wild.

Description :

Microsoft Windows Common Log File System Driver contains a privilege escalation vulnerability that could allow a local, privileged attacker to bypass certain security mechanisms.

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.

Notes :

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-43226 ; https://nvd.nist.gov/vuln/detail/CVE-2021-43226

Affected Products

The following products are affected by CVE-2021-43226 vulnerability. Even if cvefeed.io is aware of the exact versions of the products that are affected, the information is not represented in the table below.

ID Vendor Product Action
1 Microsoft windows_10
2 Microsoft windows_7
3 Microsoft windows_8.1
4 Microsoft windows_rt_8.1
5 Microsoft windows_server_2008
6 Microsoft windows_server_2012
7 Microsoft windows_server_2016
8 Microsoft windows_server_2019
9 Microsoft windows_server
10 Microsoft windows_10_1607
11 Microsoft windows_10_1809
12 Microsoft windows_10_20h2
13 Microsoft windows_10_21h2
14 Microsoft windows_server_2022
15 Microsoft windows_11_21h2
16 Microsoft windows_11
17 Microsoft windows_10_1507
18 Microsoft windows_10_21h1
19 Microsoft windows_10_1909
20 Microsoft windows_server_20h2
21 Microsoft windows_10_2004
22 Microsoft windows_server_2004
23 Microsoft windows_server_2012_r2
24 Microsoft windows_server_2008_r2
25 Microsoft windows_server_2008_sp2
: Total Affected Vendor : 1 | Products : 25
CVSS Scores
The Common Vulnerability Scoring System is a standardized framework for assessing the severity of vulnerabilities in software and systems. We collect and displays CVSS scores from various sources for each CVE.
Score Version Severity Vector Exploitability Score Impact Score Source
CVSS 2.0 MEDIUM [email protected]
CVSS 3.1 HIGH [email protected]
CVSS 3.1 HIGH [email protected]
Solution
A vulnerability in the Windows Common Log File System Driver could allow for privilege escalation.
  • Apply the latest security or cumulative updates provided by Microsoft.
  • Reboot the system if prompted during the update process.
Public PoC/Exploit Available at Github

CVE-2021-43226 has a 2 public PoC/Exploit available at Github. Go to the Public Exploits tab to see the list.

References to Advisories, Solutions, and Tools

Here, you will find a curated list of external links that provide in-depth information, practical solutions, and valuable tools related to CVE-2021-43226.

URL Resource
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-43226 Patch Vendor Advisory
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-43226 Patch Vendor Advisory
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-43226
CWE - Common Weakness Enumeration

While CVE identifies specific instances of vulnerabilities, CWE categorizes the common flaws or weaknesses that can lead to vulnerabilities. CVE-2021-43226 is associated with the following CWEs:

Common Attack Pattern Enumeration and Classification (CAPEC)

Common Attack Pattern Enumeration and Classification (CAPEC) stores attack patterns, which are descriptions of the common attributes and approaches employed by adversaries to exploit the CVE-2021-43226 weaknesses.

We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).

Profile Photo
Rosayxy/cve-2021-43226PoC

a Proof of Concept of cve-2021-43226,stack overflow in Windows driver clfs.sys

C++

Updated: 1 year, 9 months ago
2 stars 1 fork 1 watcher
Born at : Oct. 30, 2023, 6:47 a.m. This repo has been linked 1 different CVEs too.
Profile Photo
KaLendsi/CVE-2021-43224-POC

Windows Common Log File System Driver POC

C++

Updated: 7 months ago
95 stars 29 fork 29 watcher
Born at : Dec. 21, 2021, 1:51 a.m. This repo has been linked 2 different CVEs too.

Results are limited to the first 15 repositories due to potential performance issues.

The following list is the news that have been mention CVE-2021-43226 vulnerability anywhere in the article.

  • CybersecurityNews
CISA Warns of Windows Privilege Escalation Vulnerability Exploited in Attacks

CISA has issued an urgent security advisory, adding Microsoft Windows privilege escalation vulnerability CVE-2021-43226 to its Known Exploited Vulnerabilities (KEV) catalog on October 6, 2025. The vul ... Read more

Published Date: Oct 07, 2025 (3 weeks, 1 day ago)
  • TheCyberThrone
CISA Adds 7 Actively Exploited Vulnerabilities to KEV Catalog

October 7, 2025The Cybersecurity and Infrastructure Security Agency (CISA) has expanded its Known Exploited Vulnerabilities (KEV) catalog in October 2025, adding several high-impact vulnerabilities be ... Read more

Published Date: Oct 07, 2025 (3 weeks, 1 day ago)
  • Google Cloud
Ransomware Rebounds: Extortion Threat Surges in 2023, Attackers Rely on Publicly Available and Legitimate Tools

Written by: Bavi Sadayappan, Zach Riddle, Jordan Nuce, Joshua Shilko, Jeremy Kennelly A version of this blog post was published to the Mandiant Advantage portal on April 18, 2024. Executive Summary In ... Read more

Published Date: Jun 03, 2024 (1 year, 4 months ago)

Results are limited to the first 20 news articles due to potential performance issues.

The following table lists the changes that have been made to the CVE-2021-43226 vulnerability over time.

Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.

  • CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0

    Oct. 22, 2025

    Action Type Old Value New Value
    Added Reference https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-43226
  • CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0

    Oct. 21, 2025

    Action Type Old Value New Value
    Removed Reference https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-43226
  • CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0

    Oct. 21, 2025

    Action Type Old Value New Value
    Added Reference https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-43226
  • Modified Analysis by [email protected]

    Oct. 07, 2025

    Action Type Old Value New Value
    Changed CPE Configuration OR *cpe:2.3:o:microsoft:windows_server_2008:r2:sp1:*:*:*:*:x64:* *cpe:2.3:o:microsoft:windows_server_2012:r2:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_10:1607:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_8.1:-:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_server_2016:-:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_server_2008:-:sp2:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_7:-:sp1:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_rt_8.1:-:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_server_2012:-:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_10:-:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_server_2019:-:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_10:1809:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_10:1909:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_10:2004:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_server_2016:2004:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_10:20h2:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_10:21h1:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_server:20h2:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_server:2022:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_11:-:*:*:*:*:*:*:* OR *cpe:2.3:o:microsoft:windows_server_2008:r2:sp1:*:*:*:*:x64:* *cpe:2.3:o:microsoft:windows_server_2012:r2:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_8.1:-:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_7:-:sp1:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_rt_8.1:-:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_server_2012:-:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_server_2008:-:sp2:*:*:*:*:x64:* *cpe:2.3:o:microsoft:windows_server_2008:-:sp2:*:*:*:*:x86:* *cpe:2.3:o:microsoft:windows_10_1507:*:*:*:*:*:*:x86:* versions up to (excluding) 10.0.10240.19145 *cpe:2.3:o:microsoft:windows_10_1507:*:*:*:*:*:*:x64:* versions up to (excluding) 10.0.10240.19145 *cpe:2.3:o:microsoft:windows_10_1607:*:*:*:*:*:*:x86:* versions up to (excluding) 10.0.14393.4825 *cpe:2.3:o:microsoft:windows_10_1607:*:*:*:*:*:*:x64:* versions up to (excluding) 10.0.14393.4825 *cpe:2.3:o:microsoft:windows_10_1809:*:*:*:*:*:*:*:* versions up to (excluding) 10.0.17763.2366 *cpe:2.3:o:microsoft:windows_10_1909:*:*:*:*:*:*:*:* versions up to (excluding) 10.0.18363.1977 *cpe:2.3:o:microsoft:windows_10_2004:*:*:*:*:*:*:*:* versions up to (excluding) 10.0.19041.1415 *cpe:2.3:o:microsoft:windows_10_20h2:*:*:*:*:*:*:x86:* versions up to (excluding) 10.0.19042.1415 *cpe:2.3:o:microsoft:windows_10_20h2:*:*:*:*:*:*:arm64:* versions up to (excluding) 10.0.19042.1415 *cpe:2.3:o:microsoft:windows_10_21h2:*:*:*:*:*:*:*:* versions up to (excluding) 10.0.19044.1415 *cpe:2.3:o:microsoft:windows_server_2022:*:*:*:*:*:*:*:* versions up to (excluding) 10.0.20348.405 *cpe:2.3:o:microsoft:windows_server_2019:*:*:*:*:*:*:*:* versions up to (excluding) 10.0.17763.2366 *cpe:2.3:o:microsoft:windows_server_2016:*:*:*:*:*:*:*:* versions up to (excluding) 10.0.14393.4825 *cpe:2.3:o:microsoft:windows_server_2004:*:*:*:*:*:*:*:* versions up to (excluding) 10.0.19041.1415 *cpe:2.3:o:microsoft:windows_server_20h2:*:*:*:*:*:*:*:* versions up to (excluding) 10.0.19042.1415 *cpe:2.3:o:microsoft:windows_10_21h1:*:*:*:*:*:*:*:* versions up to (excluding) 10.0.19043.1415 *cpe:2.3:o:microsoft:windows_11_21h2:*:*:*:*:*:*:*:* versions up to (excluding) 10.0.22000.376
  • CVE CISA KEV Update by 9119a7d8-5eab-497f-8521-727c672e3725

    Oct. 07, 2025

    Action Type Old Value New Value
    Added Date Added 2025-10-06
    Added Due Date 2025-10-27
    Added 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.
    Added Vulnerability Name Microsoft Windows Privilege Escalation Vulnerability
  • CVE Modified by af854a3a-2127-422b-91ae-364da2661108

    Nov. 21, 2024

    Action Type Old Value New Value
    Added Reference https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-43226
  • CVE Modified by [email protected]

    May. 14, 2024

    Action Type Old Value New Value
  • CVE Modified by [email protected]

    Dec. 28, 2023

    Action Type Old Value New Value
    Changed Description Windows Common Log File System Driver Elevation of Privilege Vulnerability This CVE ID is unique from CVE-2021-43207. Windows Common Log File System Driver Elevation of Privilege Vulnerability
  • CWE Remap by [email protected]

    Jul. 12, 2022

    Action Type Old Value New Value
    Changed CWE CWE-269 NVD-CWE-noinfo
  • CPE Deprecation Remap by [email protected]

    May. 23, 2022

    Action Type Old Value New Value
    Changed CPE Configuration OR *cpe:2.3:o:microsoft:windows_server:2004:*:*:*:*:*:*:* OR *cpe:2.3:o:microsoft:windows_server_2016:2004:*:*:*:*:*:*:*
  • CPE Deprecation Remap by [email protected]

    May. 23, 2022

    Action Type Old Value New Value
    Changed CPE Configuration OR *cpe:2.3:o:microsoft:windows_server:20h2:*:*:*:*:*:*:* OR *cpe:2.3:o:microsoft:windows_10:20h2:*:*:*:*:*:*:*
  • Modified Analysis by [email protected]

    Feb. 09, 2022

    Action Type Old Value New Value
  • CVE Modified by [email protected]

    Dec. 29, 2021

    Action Type Old Value New Value
    Added CVSS V3.1 Microsoft Corporation AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
  • Initial Analysis by [email protected]

    Dec. 22, 2021

    Action Type Old Value New Value
    Added CVSS V2 NIST (AV:L/AC:L/Au:N/C:P/I:P/A:P)
    Added CVSS V3.1 NIST AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
    Changed Reference Type https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-43226 No Types Assigned https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-43226 Patch, Vendor Advisory
    Added CWE NIST CWE-269
    Added CPE Configuration OR *cpe:2.3:o:microsoft:windows_10:-:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_10:20h2:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_10:21h1:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_10:1607:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_10:1809:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_10:1909:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_10:2004:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_11:-:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_7:-:sp1:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_8.1:-:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_rt_8.1:-:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_server:20h2:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_server:2004:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_server:2022:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_server_2008:-:sp2:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_server_2008:r2:sp1:*:*:*:*:x64:* *cpe:2.3:o:microsoft:windows_server_2012:-:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_server_2012:r2:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_server_2016:-:*:*:*:*:*:*:* *cpe:2.3:o:microsoft:windows_server_2019:-:*:*:*:*:*:*:*
EPSS is a daily estimate of the probability of exploitation activity being observed over the next 30 days. Following chart shows the EPSS score history of the vulnerability.
Vulnerability Scoring Details
Base CVSS Score: 7.8
Attack Vector
Attack Complexity
Privileges Required
User Interaction
Scope
Confidentiality Impact
Integrity Impact
Availability Impact
Base CVSS Score: 4.6
Access Vector
Access Complexity
Authentication
Confidentiality Impact
Integrity Impact
Availability Impact
Exploit Prediction

EPSS is a daily estimate of the probability of exploitation activity being observed over the next 30 days.

31.88 }} -1.76%

score

0.96583

percentile