IRONSMITHINTEL
CRITICALCVSS9.8
|
Actively Exploited
|CISA KEV|CVE-2020-0646|Auth: none — unauthenticated|Reboot: required|Manual only

KB4532933: Windows Server Security Update (January 2020)

Microsoft .NET Framework contains an improper input validation vulnerability that allows for remote code execution.

Published Jan 14, 2020 · 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, 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 is a Software Vulnerability (CWE-91) (CWE-91) vulnerability in Microsoft .NET Framework. A remote code execution vulnerability exists when the Microsoft .NET Framework fails to validate input properly, aka '.NET Framework Remote Code Execution Injection Vulnerability'. 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:

●IT Security
●Running .net framework: 3.0, 3.5, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 3.5.1, 4.5.2, 4.6, 4.6.1
Fixed inKB4532933, KB4532935, KB4532936, KB4532938, KB4534271, KB4534276, KB4534293, KB4534306, KB4534976, KB4534977, KB4534978, KB4534979, KB4535101, KB4535102, KB4535103, KB4535104, KB4535105 (applies to 87 product versions)
Real-world incidentsWhat we've seen

Active exploitation documented in the wild. Threat-research write-up: http://packetstormsecurity.com/files/156930/SharePoint-Workflows-XOML-Injection.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 CatalogKB4532933

Manual remediation steps

Apply the Microsoft Security Update

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

Required KB Updates

    1
    KB4532933 — https://support.microsoft.com/help/4532933
    1
    KB4532935 — https://support.microsoft.com/help/4532935
    1
    KB4532936 — https://support.microsoft.com/help/4532936
    1
    KB4532938 — https://support.microsoft.com/help/4532938
    1
    KB4534271 — https://support.microsoft.com/help/4534271
    1
    KB4534276 — https://support.microsoft.com/help/4534276
    1
    KB4534293 — https://support.microsoft.com/help/4534293
    1
    KB4534306 — https://support.microsoft.com/help/4534306
    1
    KB4534976 — https://support.microsoft.com/help/4534976
    1
    KB4534977 — https://support.microsoft.com/help/4534977
    1
    KB4534978 — https://support.microsoft.com/help/4534978
    1
    KB4534979 — https://support.microsoft.com/help/4534979
    1
    KB4535101 — https://support.microsoft.com/help/4535101
    1
    KB4535102 — https://support.microsoft.com/help/4535102
    1
    KB4535103 — https://support.microsoft.com/help/4535103
    1
    KB4535104 — https://support.microsoft.com/help/4535104
    1
    KB4535105 — https://support.microsoft.com/help/4535105

Supersedes: KB4524741; 4533095, KB4524742; 4533096, KB4524743; 4533097, KB4524744; 4533098, KB4530681, KB4530689, KB4530714, KB4530717

Affected Products

    1
    Microsoft .NET Framework 3.0 Service Pack 2 on Windows Server 2008 for 32-bit Systems Service Pack 2
    1
    Microsoft .NET Framework 3.0 Service Pack 2 on Windows Server 2008 for Itanium-Based Systems Service Pack 2
    1
    Microsoft .NET Framework 3.0 Service Pack 2 on Windows Server 2008 for x64-based Systems Service Pack 2
    1
    Microsoft .NET Framework 3.5 AND 4.6.2/4.7/4.7.1/4.7.2 on Windows 10 Version 1607 for 32-bit Systems
    1
    Microsoft .NET Framework 3.5 AND 4.6.2/4.7/4.7.1/4.7.2 on Windows 10 Version 1607 for x64-based Systems
    1
    Microsoft .NET Framework 3.5 AND 4.6.2/4.7/4.7.1/4.7.2 on Windows Server 2016
    1
    Microsoft .NET Framework 3.5 AND 4.6.2/4.7/4.7.1/4.7.2 on Windows Server 2016 (Server Core installation)
    1
    Microsoft .NET Framework 3.5 AND 4.6/4.6.1/4.6.2 on Windows 10 for 32-bit Systems
    1
    Microsoft .NET Framework 3.5 AND 4.6/4.6.1/4.6.2 on Windows 10 for x64-based Systems
    1
    Microsoft .NET Framework 3.5 AND 4.7.1/4.7.2 on Windows 10 Version 1709 for 32-bit Systems
    1
    Microsoft .NET Framework 3.5 AND 4.7.1/4.7.2 on Windows 10 Version 1709 for x64-based Systems
    1
    Microsoft .NET Framework 3.5 AND 4.7.2 on Windows 10 Version 1803 for 32-bit Systems
    1
    Microsoft .NET Framework 3.5 AND 4.7.2 on Windows 10 Version 1803 for x64-based Systems
    1
    Microsoft .NET Framework 3.5 AND 4.7.2 on Windows 10 Version 1809 for 32-bit Systems
    1
    Microsoft .NET Framework 3.5 AND 4.7.2 on Windows 10 Version 1809 for x64-based Systems
    1
    Microsoft .NET Framework 3.5 AND 4.7.2 on Windows Server 2019
    1
    Microsoft .NET Framework 3.5 AND 4.7.2 on Windows Server 2019 (Server Core installation)
    1
    Microsoft .NET Framework 3.5 AND 4.7.2 on Windows Server, version 1803 (Server Core Installation)
    1
    Microsoft .NET Framework 3.5 AND 4.8 on Windows 10 Version 1809 for 32-bit Systems
    1
    Microsoft .NET Framework 3.5 AND 4.8 on Windows 10 Version 1809 for x64-based Systems
    1
    (…67 more product versions)

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 (may or may not be required for this update)

Microsoft Update Catalog (manual download)

1
Open https://catalog.update.microsoft.com
2
Search for KB4532933
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 KB4532933 for the affected products in your update management console.

Microsoft Download Center Links

    1
    https://catalog.update.microsoft.com/v7/site/Search.aspx?q=KB4532927
    1
    https://catalog.update.microsoft.com/v7/site/Search.aspx?q=KB4532928
    1
    https://catalog.update.microsoft.com/v7/site/Search.aspx?q=KB4532929
    1
    https://catalog.update.microsoft.com/v7/site/Search.aspx?q=KB4532930
    1
    https://catalog.update.microsoft.com/v7/site/Search.aspx?q=KB4532931
    1
    (…31 more)

Verification

Confirm the update is installed:

Get-HotFix | Where-Object { $_.HotFixID -in @('KB4532933','KB4532935','KB4532936','KB4532938','KB4534271','KB4534276','KB4534293','KB4534306','KB4534976','KB4534977','KB4534978','KB4534979','KB4535101','KB4535102','KB4535103','KB4535104','KB4535105') }

References

    1
    Microsoft Security Response Center: https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2020-0646
    1
    KB article: https://support.microsoft.com/help/4534271
    1
    KB article: https://support.microsoft.com/help/4534276
    1
    KB article: https://support.microsoft.com/help/4534293
    1
    NVD entry: https://nvd.nist.gov/vuln/detail/CVE-2020-0646
    1
    CISA KEV: https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2020-0646

Discovery Credit

Soroush Dalili (@irsdl)

PowerShell automationComing soon

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

References

↗ CVE-2020-0646↗ MSRC Advisory↗ NVD↗ KBKB4532933