IRONSMITHINTEL
HIGHCVSS7.8
|
Actively Exploited
|CISA KEV|CVE-2019-1253|Auth: low — authenticated user|Reboot: required|Manual only

KB4512578: Windows Server Security Update (September 2019)

A privilege escalation vulnerability exists when the Windows AppX Deployment Server improperly handles junctions.

Published Sep 11, 2019 · 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 2022-04-05 under CISA BOD 22-01.

How the attack worksNo clicks needed

This is a Software Vulnerability (CWE-59) (CWE-59) vulnerability in Microsoft Windows. An elevation of privilege vulnerability exists when the Windows AppX Deployment Server improperly handles junctions.To exploit this vulnerability, an attacker would first have to gain execution on the victim system, aka 'Windows Elevation of Privilege Vulnerability'. This CVE ID is unique from CVE-2019-1215, CVE-2019-1278, CVE-2019-1303. 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 1703: -; windows 10 1709: -; windows 10 1803: -; windows 10 1809: -; windows 10 1903: -; windows server 1803: -; windows server 1903: -; windows server 2019: -
Fixed inKB4512578, KB4515384, KB4516058, KB4516066, KB4516068 (applies to 18 product versions)
Real-world incidentsWhat we've seen

CISA confirms this CVE has been used in known ransomware campaigns. Added to the KEV catalog on 2022-03-15; federal agencies required to remediate by 2022-04-05.

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 CatalogKB4512578

Manual remediation steps

Apply the Microsoft Security Update

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

Required KB Updates

    1
    KB4512578 — https://support.microsoft.com/help/4512578
    1
    KB4515384 — https://support.microsoft.com/help/4515384
    1
    KB4516058 — https://support.microsoft.com/help/4516058
    1
    KB4516066 — https://support.microsoft.com/help/4516066
    1
    KB4516068 — https://support.microsoft.com/help/4516068

Supersedes: KB4511553, KB4512501, KB4512507, KB4512508, KB4512516

Affected Products

    1
    Windows 10 Version 1703 for 32-bit Systems
    1
    Windows 10 Version 1703 for x64-based Systems
    1
    Windows 10 Version 1709 for 32-bit Systems
    1
    Windows 10 Version 1709 for ARM64-based Systems
    1
    Windows 10 Version 1709 for x64-based Systems
    1
    Windows 10 Version 1803 for 32-bit Systems
    1
    Windows 10 Version 1803 for ARM64-based Systems
    1
    Windows 10 Version 1803 for x64-based Systems
    1
    Windows 10 Version 1809 for 32-bit Systems
    1
    Windows 10 Version 1809 for ARM64-based Systems
    1
    Windows 10 Version 1809 for x64-based Systems
    1
    Windows 10 Version 1903 for 32-bit Systems
    1
    Windows 10 Version 1903 for ARM64-based Systems
    1
    Windows 10 Version 1903 for x64-based Systems
    1
    Windows Server 2019
    1
    Windows Server 2019 (Server Core installation)
    1
    Windows Server, version 1803 (Server Core Installation)
    1
    Windows Server, version 1903 (Server Core installation)

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 KB4512578
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 KB4512578 for the affected products in your update management console.

Microsoft Download Center Links

    1
    https://catalog.update.microsoft.com/v7/site/Search.aspx?q=KB4512578
    1
    https://catalog.update.microsoft.com/v7/site/Search.aspx?q=KB4515384
    1
    https://catalog.update.microsoft.com/v7/site/Search.aspx?q=KB4516058
    1
    https://catalog.update.microsoft.com/v7/site/Search.aspx?q=KB4516066
    1
    https://catalog.update.microsoft.com/v7/site/Search.aspx?q=KB4516068

Verification

Confirm the update is installed:

Get-HotFix | Where-Object { $_.HotFixID -in @('KB4512578','KB4515384','KB4516058','KB4516066','KB4516068') }

References

    1
    Microsoft Security Response Center: https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2019-1253
    1
    KB article: https://support.microsoft.com/help/4512578
    1
    KB article: https://support.microsoft.com/help/4515384
    1
    KB article: https://support.microsoft.com/help/4516058
    1
    NVD entry: https://nvd.nist.gov/vuln/detail/CVE-2019-1253
    1
    CISA KEV: https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2019-1253

Discovery Credit

Abdelhamid Naceri, Zak Rogness, Gábor Selján, Zhiniang Peng (@edwardzpeng) of Qihoo 360 Core Security and Fangming Gu (@afang5472), Daniel Duggan, Zero-Point Security Ltd, Nabeel Ahmed of Dimension Data Belgium working with Trend Micro's Zero Day Initiative, Christian Danieli @padovah4ck

PowerShell automationComing soon

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

References

↗ CVE-2019-1253↗ MSRC Advisory↗ NVD↗ KBKB4512578