IRONSMITHINTEL
HIGHCVSS7.8
|
Actively Exploited
|CISA KEV|CVE-2025-59230|Auth: low — authenticated user|Reboot: required|Manual only

KB5066586: Windows Server Security Update (October 2025)

Microsoft Windows contains an improper access control vulnerability in Windows Remote Access Connection Manager which could allow an authorized attacker to elevate privileges locally.

Published Oct 14, 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 2025-11-04 under CISA BOD 22-01.

How the attack worksNo clicks needed

This is a Software Vulnerability (CWE-284) (CWE-284) vulnerability in Microsoft Windows. Improper access control in Windows Remote Access Connection Manager 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 < 10.0.10240.21161; windows 10 1607: v < 10.0.14393.8519; windows 10 1809: v < 10.0.17763.7919; windows 10 21h2: v < 10.0.19044.6456; windows 10 22h2: v < 10.0.19045.6456; windows 11 22h2: v < 10.0.22621.6060; windows 11 23h2: v ≤ 10.0.22631.6060; windows 11 24h2: v < 10.0.26100.6899; windows 11 25h2: v < 10.0.26200.6899; windows server 2008: -, r2; windows server 2012: -, r2; windows server 2016: v ≤ 10.0.14393.8519; windows server 2019: v < 10.0.17763.7919; windows server 2022: v < 10.0.20348.4294; windows server 2022 23h2: v < 10.0.25398.1913; windows server 2025: v ≤ 10.0.26100.6899
Fixed inKB5066586, KB5066780, KB5066782, KB5066791, KB5066793, KB5066835, KB5066836, KB5066837, KB5066872, KB5066873, KB5066874, KB5066875, KB5066876, KB5066877 (applies to 39 product versions) — build 10.0.10240.21161, 10.0.14393.8519+
Real-world incidentsWhat we've seen

CISA added this CVE to the Known Exploited Vulnerabilities catalog on 2025-10-14 based on evidence of active exploitation in the wild. Federal agencies required to remediate by 2025-11-04.

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 CatalogKB5066586

Manual remediation steps

Apply the Microsoft Security Update

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

Required KB Updates

    1
    KB5066586 — https://support.microsoft.com/help/5066586
    1
    KB5066780 — https://support.microsoft.com/help/5066780
    1
    KB5066782 — https://support.microsoft.com/help/5066782
    1
    KB5066791 — https://support.microsoft.com/help/5066791
    1
    KB5066793 — https://support.microsoft.com/help/5066793
    1
    KB5066835 — https://support.microsoft.com/help/5066835
    1
    KB5066836 — https://support.microsoft.com/help/5066836
    1
    KB5066837 — https://support.microsoft.com/help/5066837
    1
    KB5066872 — https://support.microsoft.com/help/5066872
    1
    KB5066873 — https://support.microsoft.com/help/5066873
    1
    KB5066874 — https://support.microsoft.com/help/5066874
    1
    KB5066875 — https://support.microsoft.com/help/5066875
    1
    KB5066876 — https://support.microsoft.com/help/5066876
    1
    KB5066877 — https://support.microsoft.com/help/5066877

Supersedes: KB5065425, KB5065426, KB5065427, KB5065428, KB5065429, KB5065430, KB5065431, KB5065432, KB5065468, KB5065507, KB5065508, KB5065509

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 11 Version 25H2 for ARM64-based Systems
    1
    Windows 11 Version 25H2 for x64-based Systems
    1
    (…19 more product versions)

Fixed Build Numbers

    1
    10.0.10240.21161
    1
    10.0.14393.8519
    1
    10.0.17763.7919
    1
    10.0.19044.6456
    1
    10.0.19045.6456
    1
    10.0.20348.4294
    1
    10.0.22621.6060
    1
    10.0.22631.6060
    1
    10.0.25398.1913
    1
    10.0.26100.6899
    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 KB5066586
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 KB5066586 for the affected products in your update management console.

Microsoft Download Center Links

    1
    https://catalog.update.microsoft.com/v7/site/Search.aspx?q=KB5066586
    1
    https://catalog.update.microsoft.com/v7/site/Search.aspx?q=KB5066780
    1
    https://catalog.update.microsoft.com/v7/site/Search.aspx?q=KB5066782
    1
    https://catalog.update.microsoft.com/v7/site/Search.aspx?q=KB5066791
    1
    https://catalog.update.microsoft.com/v7/site/Search.aspx?q=KB5066793
    1
    (…9 more)

Verification

Confirm the update is installed:

Get-HotFix | Where-Object { $_.HotFixID -in @('KB5066586','KB5066780','KB5066782','KB5066791','KB5066793','KB5066835','KB5066836','KB5066837','KB5066872','KB5066873','KB5066874','KB5066875','KB5066876','KB5066877') }

References

    1
    Microsoft Security Response Center: https://msrc.microsoft.com/update-guide/en-US/vulnerability/CVE-2025-59230
    1
    KB article: https://support.microsoft.com/help/5066586
    1
    KB article: https://support.microsoft.com/help/5066780
    1
    KB article: https://support.microsoft.com/help/5066782
    1
    NVD entry: https://nvd.nist.gov/vuln/detail/CVE-2025-59230
    1
    CISA KEV: https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-59230

Discovery Credit

Microsoft Threat Intelligence Center (MSTIC) & Microsoft Security Response Center (MSRC)

PowerShell automationComing soon

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

References

↗ CVE-2025-59230↗ MSRC Advisory↗ NVD↗ KBKB5066586