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

KB5055518: Windows Server 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 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 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
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↗ NVD↗ KBKB5055518