IRONSMITHINTEL
HIGHCVSS7.8
|
Actively Exploited
|CISA KEV|CVE-2025-21418|Auth: low — authenticated user|Reboot: required|Manual only

KB5051974: Windows Server Security Update (February 2025)

Microsoft Windows Ancillary Function Driver for WinSock contains a heap-based buffer overflow vulnerability that allows for privilege escalation, enabling a local attacker to gain SYSTEM privileges.

Published Feb 11, 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. Federal agencies are required to remediate by 2025-03-04 under CISA BOD 22-01.

How the attack worksNo clicks needed

This is a Heap-based Buffer Overflow (CWE-122) vulnerability in Microsoft Windows. Windows Ancillary Function Driver for WinSock 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 1607: v < 10.0.10240.20915; windows 10 1809: v < 10.0.17763.6893; windows 10 21h2: v < 10.0.19044.5487; windows 10 22h2: v < 10.0.19045.5487; windows 11 22h2: v < 10.0.22621.4890; windows 11 23h2: v < 10.0.22631.4890; windows 11 24h2: v < 10.0.26100.3107; windows server 2008: -, r2; windows server 2012: -, r2; windows server 2016: v < 10.0.14393.7785; windows server 2019: v < 10.0.17763.6893; windows server 2022: v < 10.0.20348.3148; windows server 2022 23h2: v < 10.0.25398.1425; windows server 2025: v < 10.0.26100.3107
Fixed inKB5051974, KB5051979, KB5051980, KB5051987, KB5051989, KB5052000, KB5052006, KB5052016, KB5052020, KB5052032, KB5052038, KB5052040, KB5052042, KB5052072, KB5052105, KB5052106 (applies to 37 product versions) — build 10.0.10240.20915, 10.0.14393.7785+
Real-world incidentsWhat we've seen

CISA added this CVE to the Known Exploited Vulnerabilities catalog on 2025-02-11 based on evidence of active exploitation in the wild. Federal agencies required to remediate by 2025-03-04.

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 CatalogKB5051974

Manual remediation steps

Apply the Microsoft Security Update

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

Required KB Updates

    1
    KB5051974 — https://support.microsoft.com/help/5051974
    1
    KB5051979 — https://support.microsoft.com/help/5051979
    1
    KB5051980 — https://support.microsoft.com/help/5051980
    1
    KB5051987 — https://support.microsoft.com/help/5051987
    1
    KB5051989 — https://support.microsoft.com/help/5051989
    1
    KB5052000 — https://support.microsoft.com/help/5052000
    1
    KB5052006 — https://support.microsoft.com/help/5052006
    1
    KB5052016 — https://support.microsoft.com/help/5052016
    1
    KB5052020 — https://support.microsoft.com/help/5052020
    1
    KB5052032 — https://support.microsoft.com/help/5052032
    1
    KB5052038 — https://support.microsoft.com/help/5052038
    1
    KB5052040 — https://support.microsoft.com/help/5052040
    1
    KB5052042 — https://support.microsoft.com/help/5052042
    1
    KB5052072 — https://support.microsoft.com/help/5052072
    1
    KB5052105 — https://support.microsoft.com/help/5052105
    1
    KB5052106 — https://support.microsoft.com/help/5052106

Supersedes: KB5049981, KB5049983, KB5049984, KB5049993, KB5050004, KB5050008, KB5050009, KB5050013, KB5050021, KB5050048, KB5050049, KB5050063

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
    10.0.10240.20915
    1
    10.0.14393.7785
    1
    10.0.17763.6893
    1
    10.0.19044.5487
    1
    10.0.19045.5487
    1
    10.0.20348.3148
    1
    10.0.20348.3207
    1
    10.0.22621.4890
    1
    10.0.22631.4890
    1
    10.0.25398.1425
    1
    (…6 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 KB5051974
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 KB5051974 for the affected products in your update management console.

Microsoft Download Center Links

    1
    https://catalog.update.microsoft.com/v7/site/Search.aspx?q=KB5051974
    1
    https://catalog.update.microsoft.com/v7/site/Search.aspx?q=KB5051979
    1
    https://catalog.update.microsoft.com/v7/site/Search.aspx?q=KB5051980
    1
    https://catalog.update.microsoft.com/v7/site/Search.aspx?q=KB5051987
    1
    https://catalog.update.microsoft.com/v7/site/Search.aspx?q=KB5051989
    1
    (…9 more)

Verification

Confirm the update is installed:

Get-HotFix | Where-Object { $_.HotFixID -in @('KB5051974','KB5051979','KB5051980','KB5051987','KB5051989','KB5052000','KB5052006','KB5052016','KB5052020','KB5052032','KB5052038','KB5052040','KB5052042','KB5052072','KB5052105','KB5052106') }

References

    1
    Microsoft Security Response Center: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-21418
    1
    KB article: https://support.microsoft.com/help/5051974
    1
    KB article: https://support.microsoft.com/help/5051979
    1
    KB article: https://support.microsoft.com/help/5051980
    1
    NVD entry: https://nvd.nist.gov/vuln/detail/CVE-2025-21418
    1
    CISA KEV: https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-21418

Discovery Credit

Anonymous

PowerShell automationComing soon

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

References

↗ CVE-2025-21418↗ MSRC Advisory↗ NVD↗ KBKB5051974