IRONSMITHINTEL
HIGHCVSS7.8
|
Actively Exploited
|CISA KEV|CVE-2020-0938|Auth: none — unauthenticated|Reboot: required|Manual only

KB4549949: Windows Server Security Update (April 2020)

Microsoft Windows Adobe Font Manager Library contains an unspecified vulnerability when handling specially crafted multi-master fonts (Adobe Type 1 PostScript format) that allows for remote code execution for all systems except Windows 10. For systems running Windows 10, an attacker who successfully exploited the vulnerability could execute code in an AppContainer sandbox context with limited privileges and capabilities.

Published Apr 15, 2020 · Updated May 16, 2026
Why patchRisk explained in plain English
Worst-case scenarioIf unpatched

A local 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 Out-of-bounds Write (CWE-787) vulnerability in Microsoft Windows. A remote code execution vulnerability exists in Microsoft Windows when the Windows Adobe Type Manager Library improperly handles a specially-crafted multi-master font - Adobe Type 1 PostScript format.For all systems except Windows 10, an attacker who successfully exploited the vulnerability could execute code remotely, aka 'Adobe Font Manager Library Remote Code Execution Vulnerability'. This CVE ID is unique from CVE-2020-1020. Exploitation requires local access, low attack complexity, no authentication required, and 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: -; windows 10 1607: -; windows 10 1709: -; windows 10 1803: -; windows 10 1809: -; windows 10 1903: -; windows 10 1909: -; windows 7: -; windows 8.1: -; windows rt 8.1: -; windows server 1803: -; windows server 1903: -; windows server 1909: -; windows server 2008: -, r2; windows server 2012: -, r2; windows server 2016: -; windows server 2019: -
Fixed inKB4549949, KB4549951, KB4550917, KB4550922, KB4550927, KB4550929, KB4550930, KB4550951, KB4550957, KB4550961, KB4550964, KB4550965, KB4550970, KB4550971 (applies to 41 product versions)
Real-world incidentsWhat we've seen

CISA added this CVE to the Known Exploited Vulnerabilities catalog on 2021-11-03 based on evidence of active exploitation in the wild. Federal agencies required to remediate by 2022-05-03.

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 CatalogKB4549949

Manual remediation steps

Apply the Microsoft Security Update

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

Required KB Updates

    1
    KB4549949 — https://support.microsoft.com/help/4549949
    1
    KB4549951 — https://support.microsoft.com/help/4549951
    1
    KB4550917 — https://support.microsoft.com/help/4550917
    1
    KB4550922 — https://support.microsoft.com/help/4550922
    1
    KB4550927 — https://support.microsoft.com/help/4550927
    1
    KB4550929 — https://support.microsoft.com/help/4550929
    1
    KB4550930 — https://support.microsoft.com/help/4550930
    1
    KB4550951 — https://support.microsoft.com/help/4550951
    1
    KB4550957 — https://support.microsoft.com/help/4550957
    1
    KB4550961 — https://support.microsoft.com/help/4550961
    1
    KB4550964 — https://support.microsoft.com/help/4550964
    1
    KB4550965 — https://support.microsoft.com/help/4550965
    1
    KB4550970 — https://support.microsoft.com/help/4550970
    1
    KB4550971 — https://support.microsoft.com/help/4550971

Supersedes: KB4538461, KB4540670, KB4540673, KB4540681, KB4540688, KB4540689, KB4540693, KB4541506, KB4541509, KB4541510

Affected Products

    1
    Windows 10 Version 1607 for 32-bit Systems
    1
    Windows 10 Version 1607 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 10 Version 1909 for 32-bit Systems
    1
    Windows 10 Version 1909 for ARM64-based Systems
    1
    Windows 10 Version 1909 for x64-based Systems
    1
    Windows 10 for 32-bit Systems
    1
    Windows 10 for x64-based Systems
    1
    Windows 7 for 32-bit Systems Service Pack 1
    1
    (…21 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 — a reboot IS required to complete the install

Microsoft Update Catalog (manual download)

1
Open https://catalog.update.microsoft.com
2
Search for KB4549949
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 KB4549949 for the affected products in your update management console.

Microsoft Download Center Links

    1
    https://catalog.update.microsoft.com/v7/site/Search.aspx?q=KB4549949
    1
    https://catalog.update.microsoft.com/v7/site/Search.aspx?q=KB4549951
    1
    https://catalog.update.microsoft.com/v7/site/Search.aspx?q=KB4550917
    1
    https://catalog.update.microsoft.com/v7/site/Search.aspx?q=KB4550922
    1
    https://catalog.update.microsoft.com/v7/site/Search.aspx?q=KB4550927
    1
    (…9 more)

Verification

Confirm the update is installed:

Get-HotFix | Where-Object { $_.HotFixID -in @('KB4549949','KB4549951','KB4550917','KB4550922','KB4550927','KB4550929','KB4550930','KB4550951','KB4550957','KB4550961','KB4550964','KB4550965','KB4550970','KB4550971') }

References

    1
    Microsoft Security Response Center: https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2020-0938
    1
    KB article: https://support.microsoft.com/help/4549949
    1
    KB article: https://support.microsoft.com/help/4550917
    1
    KB article: https://support.microsoft.com/help/4550922
    1
    NVD entry: https://nvd.nist.gov/vuln/detail/CVE-2020-0938
    1
    CISA KEV: https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2020-0938

Discovery Credit

Liubenjin and Zhiyi Zhang from Codesafe Team of Legendsec at Qi'anxin Group, Google: Project Zero and Threat Analysis Group

PowerShell automationComing soon

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

References

↗ CVE-2020-0938↗ MSRC Advisory↗ NVD↗ KBKB4549949