IRONSMITHINTEL
HIGHCVSS7.8
|
Actively Exploited
|CISA KEV|CVE-2025-29824|Auth: low — authenticated user|Reboot: required|Manual only

KB5055518: Windows Server 2019 / 2022 / 2025 +more Security Update (April 2025)

Microsoft Windows Common Log File System (CLFS) Driver contains a use-after-free vulnerability that allows an authorized attacker to elevate privileges locally.

Published Apr 8, 2025 · Updated Jun 10, 2026
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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 2025-04-29 under CISA BOD 22-01.

How the attack worksNo clicks needed

This is a Use After Free (CWE-416) vulnerability in Microsoft Windows. Use after free in Windows Common Log File System Driver allows an authorized attacker to elevate privileges locally. 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 < 10.0.10240.20978; windows 10 1607: v < 10.0.14393.7969; windows 10 1809: v < 10.0.17763.7136; windows 10 21h2: v < 10.0.19044.5737; windows 10 22h2: v < 10.0.19045.5737; windows 11 22h2: v < 10.0.22621.5189; windows 11 23h2: v < 10.0.22631.5189; windows 11 24h2: v < 10.0.26100.3775; windows server 2008: -, r2; windows server 2012: -, r2; windows server 2016: v < 10.0.14393.7969; windows server 2019: v < 10.0.17763.7136; windows server 2022: v < 10.0.20348.3453; windows server 2022 23h2: v < 10.0.25398.1551; windows server 2025: v < 10.0.26100.3775

Affected OS versions

Windows Server 2019Windows Server 2022Windows Server 2025Windows Server 2016Windows Server 2012 R2
Fixed inKB5055518, KB5055519, KB5055521, KB5055523, KB5055526, KB5055527, KB5055528, KB5055547, KB5055557, KB5055561, KB5055570, KB5055581, KB5055596, KB5055609 (applies to 37 product versions) — build 10.0.10240.20978, 10.0.14393.7969+
Real-world incidentsWhat we've seen

Used in known ransomware campaigns. Threat-research write-up: https://www.vicarius.io/vsociety/posts/cve-2025-29824-windows-common-log-file-system-driver-elevation-of-privilege-vulnerability-detection-script

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 CatalogKB5055518

Manual remediation steps

Apply the Microsoft Security Update

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

Required KB Updates

    1
    KB5055518 — https://support.microsoft.com/help/5055518
    1
    KB5055519 — https://support.microsoft.com/help/5055519
    1
    KB5055521 — https://support.microsoft.com/help/5055521
    1
    KB5055523 — https://support.microsoft.com/help/5055523
    1
    KB5055526 — https://support.microsoft.com/help/5055526
    1
    KB5055527 — https://support.microsoft.com/help/5055527
    1
    KB5055528 — https://support.microsoft.com/help/5055528
    1
    KB5055547 — https://support.microsoft.com/help/5055547
    1
    KB5055557 — https://support.microsoft.com/help/5055557
    1
    KB5055561 — https://support.microsoft.com/help/5055561
    1
    KB5055570 — https://support.microsoft.com/help/5055570
    1
    KB5055581 — https://support.microsoft.com/help/5055581
    1
    KB5055596 — https://support.microsoft.com/help/5055596
    1
    KB5055609 — https://support.microsoft.com/help/5055609

Supersedes: KB5053594, KB5053596, KB5053598, KB5053599, KB5053602, KB5053603, KB5053606, KB5053618, KB5053620, KB5053886, KB5053887, KB5053888

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 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 Version 22H2 for 32-bit Systems
    1
    Windows 10 Version 22H2 for ARM64-based Systems
    1
    Windows 10 Version 22H2 for x64-based Systems
    1
    Windows 10 for 32-bit Systems
    1
    Windows 10 for x64-based Systems
    1
    Windows 11 Version 22H2 for ARM64-based Systems
    1
    Windows 11 Version 22H2 for x64-based Systems
    1
    Windows 11 Version 23H2 for ARM64-based Systems
    1
    Windows 11 Version 23H2 for x64-based Systems
    1
    Windows 11 Version 24H2 for ARM64-based Systems
    1
    Windows 11 Version 24H2 for x64-based Systems
    1
    Windows Server 2008 R2 for x64-based Systems Service Pack 1
    1
    Windows Server 2008 R2 for x64-based Systems Service Pack 1 (Server Core installation)
    1
    (…17 more product versions)

Fixed Build Numbers

    1
    10.0.10240.20978
    1
    10.0.14393.7969
    1
    10.0.17763.7136
    1
    10.0.19044.5737
    1
    10.0.19045.5737
    1
    10.0.20348.3453
    1
    10.0.22621.5189
    1
    10.0.22631.5189
    1
    10.0.25398.1551
    1
    10.0.26100.3775
    1
    (…4 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 KB5055518
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 KB5055518 for the affected products in your update management console.

Microsoft Download Center Links

    1
    https://catalog.update.microsoft.com/v7/site/Search.aspx?q=KB5055518
    1
    https://catalog.update.microsoft.com/v7/site/Search.aspx?q=KB5055519
    1
    https://catalog.update.microsoft.com/v7/site/Search.aspx?q=KB5055521
    1
    https://catalog.update.microsoft.com/v7/site/Search.aspx?q=KB5055523
    1
    https://catalog.update.microsoft.com/v7/site/Search.aspx?q=KB5055526
    1
    (…9 more)

Verification

Confirm the update is installed:

Get-HotFix | Where-Object { $_.HotFixID -in @('KB5055518','KB5055519','KB5055521','KB5055523','KB5055526','KB5055527','KB5055528','KB5055547','KB5055557','KB5055561','KB5055570','KB5055581','KB5055596','KB5055609') }

References

    1
    Microsoft Security Response Center: https://msrc.microsoft.com/update-guide/en-US/vulnerability/CVE-2025-29824
    1
    KB article: https://support.microsoft.com/help/5055518
    1
    KB article: https://support.microsoft.com/help/5055519
    1
    KB article: https://support.microsoft.com/help/5055521
    1
    NVD entry: https://nvd.nist.gov/vuln/detail/CVE-2025-29824
    1
    CISA KEV: https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-29824

Discovery Credit

Microsoft Threat Intelligence Center

PowerShell automationComing soon

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

References

↗ CVE-2025-29824↗ MSRC Advisory↗ KBKB5055518

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