IRONSMITHINTEL
HIGHCVSS7.8
|
Actively Exploited
|CISA KEV|CVE-2019-0808|Auth: low — authenticated user|Reboot: required|Manual only

KB4489876: Windows Server Security Update (April 2019)

Microsoft Win32k contains a privilege escalation vulnerability due to the component failing to properly handle objects in memory. Successful exploitation allows an attacker to run code in kernel mode.

Published Apr 9, 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. Federal agencies are required to remediate by 2022-05-03 under CISA BOD 22-01.

How the attack worksNo clicks needed

This vulnerability affects Microsoft Win32k. An elevation of privilege vulnerability exists in Windows when the Win32k component fails to properly handle objects in memory, aka 'Win32k Elevation of Privilege Vulnerability'. This CVE ID is unique from CVE-2019-0797. 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:

●IT Security
●Running windows 7: -; windows server 2008: -, r2
Fixed inKB4489876, KB4489878, KB4489880, KB4489885 (applies to 10 product versions)
Real-world incidentsWhat we've seen

Active exploitation documented in the wild. Threat-research write-up: http://packetstormsecurity.com/files/157616/Microsoft-Windows-NtUserMNDragOver-Local-Privilege-Escalation.html

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 CatalogKB4489876

Manual remediation steps

Apply the Microsoft Security Update

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

Required KB Updates

    1
    KB4489876 — https://support.microsoft.com/help/4489876
    1
    KB4489878 — https://support.microsoft.com/help/4489878
    1
    KB4489880 — https://support.microsoft.com/help/4489880
    1
    KB4489885 — https://support.microsoft.com/help/4489885

Supersedes: KB4486563, KB4487019, KB4487023

Affected Products

    1
    Windows 7 for 32-bit Systems Service Pack 1
    1
    Windows 7 for x64-based Systems Service Pack 1
    1
    Windows Server 2008 R2 for Itanium-Based Systems Service Pack 1
    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 Itanium-Based Systems Service Pack 2
    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)

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 KB4489876
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 KB4489876 for the affected products in your update management console.

Microsoft Download Center Links

    1
    https://catalog.update.microsoft.com/v7/site/Search.aspx?q=KB4489876
    1
    https://catalog.update.microsoft.com/v7/site/Search.aspx?q=KB4489878
    1
    https://catalog.update.microsoft.com/v7/site/Search.aspx?q=KB4489880
    1
    https://catalog.update.microsoft.com/v7/site/Search.aspx?q=KB4489885

Verification

Confirm the update is installed:

Get-HotFix | Where-Object { $_.HotFixID -in @('KB4489876','KB4489878','KB4489880','KB4489885') }

References

    1
    Microsoft Security Response Center: https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2019-0808
    1
    KB article: https://support.microsoft.com/help/4489878
    1
    KB article: https://support.microsoft.com/help/4489885
    1
    NVD entry: https://nvd.nist.gov/vuln/detail/CVE-2019-0808
    1
    CISA KEV: https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2019-0808

Discovery Credit

Clément Lecigne of Google’s Threat Analysis Group

PowerShell automationComing soon

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

References

↗ CVE-2019-0808↗ MSRC Advisory↗ NVD↗ KBKB4489876