IRONSMITHINTEL
HIGHCVSS7.5
|
Actively Exploited
|CISA KEV|CVE-2021-36942|Auth: none — unauthenticated|Reboot: required|Manual only

KB5005030: Windows Server Security Update (August 2021)

Microsoft Windows Local Security Authority (LSA) contains a spoofing vulnerability allowing an unauthenticated attacker to call a method on the LSARPC interface and coerce the domain controller to authenticate against another server using NTLM.

Published Aug 12, 2021 · Updated May 16, 2026
Why patchRisk explained in plain English
Worst-case scenarioIf unpatched

A remote attacker, without authentication, can achieve full data confidentiality loss. CISA has confirmed use of this vulnerability in known ransomware campaigns — treat as high priority for remediation. Federal agencies are required to remediate by 2021-11-17 under CISA BOD 22-01.

How the attack worksNo clicks needed

This vulnerability affects Microsoft Windows. Exploitation requires remote network access, low attack complexity, no authentication required, and no user interaction required.

📧

Phishing link

→

🖼

Malicious file

🔓

Server compromised

Am I affected?Quick check

Probably yes if any of these apply:

●Windows Administrators
●Systems Engineers
●IT Security
●Running windows server 2004: v < 10.0.19041.1165; windows server 2008: -, r2; windows server 2012: -, r2; windows server 2016: v < 10.0.14393.4583; windows server 2019: v < 10.0.17763.2114; windows server 20h2: v < 10.0.19042.1165
Fixed inKB5005030, KB5005033, KB5005043, KB5005076, KB5005088, KB5005089, KB5005090, KB5005094, KB5005095, KB5005099, KB5005106 (applies to 16 product versions) — build 10.0.14393.4583, 10.0.17763.2114+
Real-world incidentsWhat we've seen

Used in known ransomware campaigns. Threat-research write-up: https://www.kb.cert.org/vuls/id/405600

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 CatalogKB5005030

Manual remediation steps

Apply the Microsoft Security Update

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

Required KB Updates

    1
    KB5005030 — https://support.microsoft.com/help/5005030
    1
    KB5005033 — https://support.microsoft.com/help/5005033
    1
    KB5005043 — https://support.microsoft.com/help/5005043
    1
    KB5005076 — https://support.microsoft.com/help/5005076
    1
    KB5005088 — https://support.microsoft.com/help/5005088
    1
    KB5005089 — https://support.microsoft.com/help/5005089
    1
    KB5005090 — https://support.microsoft.com/help/5005090
    1
    KB5005094 — https://support.microsoft.com/help/5005094
    1
    KB5005095 — https://support.microsoft.com/help/5005095
    1
    KB5005099 — https://support.microsoft.com/help/5005099
    1
    KB5005106 — https://support.microsoft.com/help/5005106

Supersedes: KB5004237, KB5004238, KB5004244, KB5004289, KB5004294, KB5004298, KB5004305

Affected Products

    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
    Windows Server 2008 for 32-bit Systems Service Pack 2
    1
    Windows Server 2008 for 32-bit Systems Service Pack 2 (Server Core installation)
    1
    Windows Server 2008 for x64-based Systems Service Pack 2
    1
    Windows Server 2008 for x64-based Systems Service Pack 2 (Server Core installation)
    1
    Windows Server 2012
    1
    Windows Server 2012 (Server Core installation)
    1
    Windows Server 2012 R2
    1
    Windows Server 2012 R2 (Server Core installation)
    1
    Windows Server 2016
    1
    Windows Server 2016 (Server Core installation)
    1
    Windows Server 2019
    1
    Windows Server 2019 (Server Core installation)
    1
    Windows Server, version 2004 (Server Core installation)
    1
    Windows Server, version 20H2 (Server Core Installation)

Fixed Build Numbers

    1
    10.0.14393.4583
    1
    10.0.17763.2114
    1
    10.0.19041.1165
    1
    10.0.19042.1165
    1
    6.0.6003.21192
    1
    6.1.7601.25685
    1
    6.2.9200.23435
    1
    6.3.9600.20094

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 KB5005030
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 KB5005030 for the affected products in your update management console.

Microsoft Download Center Links

    1
    https://catalog.update.microsoft.com/v7/site/Search.aspx?q=KB5005030
    1
    https://catalog.update.microsoft.com/v7/site/Search.aspx?q=KB5005033
    1
    https://catalog.update.microsoft.com/v7/site/Search.aspx?q=KB5005043
    1
    https://catalog.update.microsoft.com/v7/site/Search.aspx?q=KB5005076
    1
    https://catalog.update.microsoft.com/v7/site/Search.aspx?q=KB5005088
    1
    (…6 more)

Verification

Confirm the update is installed:

Get-HotFix | Where-Object { $_.HotFixID -in @('KB5005030','KB5005033','KB5005043','KB5005076','KB5005088','KB5005089','KB5005090','KB5005094','KB5005095','KB5005099','KB5005106') }

References

    1
    Microsoft Security Response Center: https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-36942
    1
    KB article: https://support.microsoft.com/help/5005030
    1
    KB article: https://support.microsoft.com/help/5005033
    1
    KB article: https://support.microsoft.com/help/5005076
    1
    NVD entry: https://nvd.nist.gov/vuln/detail/CVE-2021-36942
    1
    CISA KEV: https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-36942
PowerShell automationComing soon

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

References

↗ CVE-2021-36942↗ MSRC Advisory↗ NVD↗ KBKB5005030