IRONSMITHINTEL
HIGHCVSS7.8
|
Actively Exploited
|CISA KEV|CVE-2022-24521|Auth: low — authenticated user|Reboot: required|Manual only

KB5012591: Windows Server Security Update (April 2022)

Microsoft Windows Common Log File System (CLFS) Driver contains an unspecified vulnerability that allows for privilege escalation.

Published Apr 15, 2022 · 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. CISA has confirmed use of this vulnerability in known ransomware campaigns — treat as high priority for remediation. Federal agencies are required to remediate by 2022-05-04 under CISA BOD 22-01.

How the attack worksNo clicks needed

This is a Out-of-bounds Write (CWE-787) vulnerability in 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 < 10.0.10240.19265; windows 10 1607: v < 10.0.14393.5066; windows 10 1809: v ≤ 10.0.17763.2803; windows 10 1909: v < 10.0.18363.2212; windows 10 20h2: v < 10.0.19042.1645; windows 10 21h1: v < 10.0.19043.1645; windows 10 21h2: v < 10.0.19044.1645; windows 11 21h2: v < 10.0.22000.613; windows 7: -; windows 8.1: -; windows rt 8.1: -; windows server 2008: r2; windows server 2012: -, r2; windows server 2016: v < 10.0.14393.5066; windows server 2019: v < 10.0.17763.2803; windows server 2022: v < 10.0.20348.643; windows server 20h2: v < 10.0.19042.1645
Fixed inKB5012591, KB5012592, KB5012596, KB5012599, KB5012604, KB5012626, KB5012632, KB5012639, KB5012647, KB5012649, KB5012650, KB5012653, KB5012658, KB5012666, KB5012670 (applies to 42 product versions) — build 10.0.10240.19265, 10.0.14393.5066+
Real-world incidentsWhat we've seen

CISA confirms this CVE has been used in known ransomware campaigns. Added to the KEV catalog on 2022-04-13; federal agencies required to remediate by 2022-05-04.

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 CatalogKB5012591

Manual remediation steps

Apply the Microsoft Security Update

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

Required KB Updates

    1
    KB5012591 — https://support.microsoft.com/help/5012591
    1
    KB5012592 — https://support.microsoft.com/help/5012592
    1
    KB5012596 — https://support.microsoft.com/help/5012596
    1
    KB5012599 — https://support.microsoft.com/help/5012599
    1
    KB5012604 — https://support.microsoft.com/help/5012604
    1
    KB5012626 — https://support.microsoft.com/help/5012626
    1
    KB5012632 — https://support.microsoft.com/help/5012632
    1
    KB5012639 — https://support.microsoft.com/help/5012639
    1
    KB5012647 — https://support.microsoft.com/help/5012647
    1
    KB5012649 — https://support.microsoft.com/help/5012649
    1
    KB5012650 — https://support.microsoft.com/help/5012650
    1
    KB5012653 — https://support.microsoft.com/help/5012653
    1
    KB5012658 — https://support.microsoft.com/help/5012658
    1
    KB5012666 — https://support.microsoft.com/help/5012666
    1
    KB5012670 — https://support.microsoft.com/help/5012670

Supersedes: KB5011485, KB5011487, KB5011491, KB5011493, KB5011495, KB5011497, KB5011503, KB5011534, KB5011535, KB5011552, KB5011564

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 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
    Windows 10 for x64-based Systems
    1
    Windows 11 version 21H2 for ARM64-based Systems
    1
    Windows 11 version 21H2 for x64-based Systems
    1
    (…22 more product versions)

Fixed Build Numbers

    1
    10.0.10240.19265
    1
    10.0.14393.5066
    1
    10.0.17763.2803
    1
    10.0.18363.2212
    1
    10.0.19042.1645
    1
    10.0.19043.1645
    1
    10.0.19044.1645
    1
    10.0.20348.643
    1
    10.0.22000.613
    1
    6.0.6003.21446
    1
    (…3 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 KB5012591
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 KB5012591 for the affected products in your update management console.

Microsoft Download Center Links

    1
    https://catalog.update.microsoft.com/v7/site/Search.aspx?q=KB5012591
    1
    https://catalog.update.microsoft.com/v7/site/Search.aspx?q=KB5012592
    1
    https://catalog.update.microsoft.com/v7/site/Search.aspx?q=KB5012596
    1
    https://catalog.update.microsoft.com/v7/site/Search.aspx?q=KB5012599
    1
    https://catalog.update.microsoft.com/v7/site/Search.aspx?q=KB5012604
    1
    (…10 more)

Verification

Confirm the update is installed:

Get-HotFix | Where-Object { $_.HotFixID -in @('KB5012591','KB5012592','KB5012596','KB5012599','KB5012604','KB5012626','KB5012632','KB5012639','KB5012647','KB5012649','KB5012650','KB5012653','KB5012658','KB5012666','KB5012670') }

References

    1
    Microsoft Security Response Center: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2022-24521
    1
    KB article: https://support.microsoft.com/help/5012591
    1
    KB article: https://support.microsoft.com/help/5012592
    1
    KB article: https://support.microsoft.com/help/5012596
    1
    NVD entry: https://nvd.nist.gov/vuln/detail/CVE-2022-24521
    1
    CISA KEV: https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2022-24521

Discovery Credit

Adam Podlosky and Amir Bazine of Crowdstrike, National Security Agency

PowerShell automationComing soon

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

References

↗ CVE-2022-24521↗ MSRC Advisory↗ NVD↗ KBKB5012591