IRONSMITHINTEL
HIGHCVSS7.8
|
Actively Exploited
|CISA KEV|CVE-2021-43226|Auth: low — authenticated user|Reboot: required|Manual only

KB5008206: Windows Server Security Update (December 2021)

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

Published Dec 15, 2021 · Updated May 16, 2026
Why patchRisk explained in plain English
Worst-case scenarioIf unpatched

A local attacker, with a low-privilege account, can achieve full data confidentiality loss, arbitrary modification of data, complete denial of service or system unavailability. Federal agencies are required to remediate by 2025-10-27 under CISA BOD 22-01.

How the attack worksNo clicks needed

This vulnerability affects Microsoft Windows. Windows Common Log File System Driver Elevation of Privilege Vulnerability Exploitation requires local access, low attack complexity, a low-privilege authenticated account, and no user interaction required.

Am I affected?Quick check

Probably yes if any of these apply:

●Windows Administrators
●Systems Engineers
●IT Security
●Running windows 10 1507: v < 10.0.10240.19145; windows 10 1607: v < 10.0.14393.4825; windows 10 1809: v < 10.0.17763.2366; windows 10 1909: v < 10.0.18363.1977; windows 10 2004: v < 10.0.19041.1415; windows 10 20h2: v < 10.0.19042.1415; windows 10 21h1: v < 10.0.19043.1415; windows 10 21h2: v < 10.0.19044.1415; windows 11 21h2: v < 10.0.22000.376; windows 7: -; windows 8.1: -; windows rt 8.1: -; windows server 2004: v < 10.0.19041.1415; windows server 2008: -, r2; windows server 2012: -, r2; windows server 2016: v < 10.0.14393.4825; windows server 2019: v < 10.0.17763.2366; windows server 2022: v < 10.0.20348.405; windows server 20h2: v < 10.0.19042.1415
Fixed inKB5008206, KB5008207, KB5008212, KB5008215, KB5008218, KB5008223, KB5008230, KB5008244, KB5008255, KB5008263, KB5008271, KB5008274, KB5008277, KB5008282, KB5008285 (applies to 46 product versions) — build 10.0.10240.19145, 10.0.14393.4825+
Real-world incidentsWhat we've seen

CISA added this CVE to the Known Exploited Vulnerabilities catalog on 2025-10-06 based on evidence of active exploitation in the wild. Federal agencies required to remediate by 2025-10-27.

How to patch

Manual download

For air-gapped servers or out-of-band deployment. Microsoft Update Catalog returns every OS-version variant of this update.

↗ Microsoft Update CatalogKB5008206

Manual remediation steps

Apply the Microsoft Security Update

Microsoft has released an official security update that fixes this vulnerability.

Required KB Updates

    1
    KB5008206 — https://support.microsoft.com/help/5008206
    1
    KB5008207 — https://support.microsoft.com/help/5008207
    1
    KB5008212 — https://support.microsoft.com/help/5008212
    1
    KB5008215 — https://support.microsoft.com/help/5008215
    1
    KB5008218 — https://support.microsoft.com/help/5008218
    1
    KB5008223 — https://support.microsoft.com/help/5008223
    1
    KB5008230 — https://support.microsoft.com/help/5008230
    1
    KB5008244 — https://support.microsoft.com/help/5008244
    1
    KB5008255 — https://support.microsoft.com/help/5008255
    1
    KB5008263 — https://support.microsoft.com/help/5008263
    1
    KB5008271 — https://support.microsoft.com/help/5008271
    1
    KB5008274 — https://support.microsoft.com/help/5008274
    1
    KB5008277 — https://support.microsoft.com/help/5008277
    1
    KB5008282 — https://support.microsoft.com/help/5008282
    1
    KB5008285 — https://support.microsoft.com/help/5008285

Supersedes: KB5007186, KB5007189, KB5007192, KB5007205, KB5007206, KB5007207, KB5007215, KB5007236, KB5007247, KB5007260, KB5007263

Affected Products

    1
    Windows 10 Version 1607 for 32-bit Systems
    1
    Windows 10 Version 1607 for x64-based Systems
    1
    Windows 10 Version 1809 for 32-bit Systems
    1
    Windows 10 Version 1809 for ARM64-based Systems
    1
    Windows 10 Version 1809 for x64-based Systems
    1
    Windows 10 Version 1909 for 32-bit Systems
    1
    Windows 10 Version 1909 for ARM64-based Systems
    1
    Windows 10 Version 1909 for x64-based Systems
    1
    Windows 10 Version 2004 for 32-bit Systems
    1
    Windows 10 Version 2004 for ARM64-based Systems
    1
    Windows 10 Version 2004 for x64-based Systems
    1
    Windows 10 Version 20H2 for 32-bit Systems
    1
    Windows 10 Version 20H2 for ARM64-based Systems
    1
    Windows 10 Version 21H1 for 32-bit Systems
    1
    Windows 10 Version 21H1 for ARM64-based Systems
    1
    Windows 10 Version 21H1 for x64-based Systems
    1
    Windows 10 Version 21H2 for 32-bit Systems
    1
    Windows 10 Version 21H2 for ARM64-based Systems
    1
    Windows 10 Version 21H2 for x64-based Systems
    1
    Windows 10 for 32-bit Systems
    1
    (…26 more product versions)

Fixed Build Numbers

    1
    10.0.10240.19145
    1
    10.0.14393.4825
    1
    10.0.17763.2366
    1
    10.0.18363.1977
    1
    10.0.19041.1415
    1
    10.0.19042.1415
    1
    10.0.19043.1415
    1
    10.0.19044.1415
    1
    10.0.20348.405
    1
    10.0.22000.376
    1
    (…5 more builds)

Installation Methods

Windows Update (recommended)

1
Settings → Windows Update → Check for updates
2
The security update is offered if your system is in scope
3
Restart when prompted — a reboot IS required to complete the install

Microsoft Update Catalog (manual download)

1
Open https://catalog.update.microsoft.com
2
Search for KB5008206
3
Download the package matching your OS architecture and Windows build
4
Run the .msu installer with administrator privileges
5
Restart when prompted

WSUS / SCCM / Intune

Approve KB5008206 for the affected products in your update management console.

Microsoft Download Center Links

    1
    https://catalog.update.microsoft.com/v7/site/Search.aspx?q=KB5008206
    1
    https://catalog.update.microsoft.com/v7/site/Search.aspx?q=KB5008207
    1
    https://catalog.update.microsoft.com/v7/site/Search.aspx?q=KB5008212
    1
    https://catalog.update.microsoft.com/v7/site/Search.aspx?q=KB5008215
    1
    https://catalog.update.microsoft.com/v7/site/Search.aspx?q=KB5008218
    1
    (…10 more)

Verification

Confirm the update is installed:

Get-HotFix | Where-Object { $_.HotFixID -in @('KB5008206','KB5008207','KB5008212','KB5008215','KB5008218','KB5008223','KB5008230','KB5008244','KB5008255','KB5008263','KB5008271','KB5008274','KB5008277','KB5008282','KB5008285') }

References

    1
    Microsoft Security Response Center: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-43226
    1
    KB article: https://support.microsoft.com/help/5008207
    1
    KB article: https://support.microsoft.com/help/5008212
    1
    KB article: https://support.microsoft.com/help/5008218
    1
    NVD entry: https://nvd.nist.gov/vuln/detail/CVE-2021-43226
    1
    CISA KEV: https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-43226

Discovery Credit

JeongOh Kyea with THEORI

PowerShell automationComing soon

No tested PowerShell script for this entry yet. We’re prioritising automation based on user demand.

References

↗ CVE-2021-43226↗ MSRC Advisory↗ NVD↗ KBKB5008206