Microsoft Windows Adobe Type Manager Library Remote Code Execution Vulnerability (CVE-2020-0938)
Executive & SecOps Summary
SECOPS ASSESSMENTWindows client operating systems prior to Windows 10, and Windows Server editions
Remote code execution with kernel-level privileges via a specially crafted Adobe Type 1 PostScript font file
Apply official Microsoft security updates immediately, or implement workarounds including disabling ATMFD.dll and stopping the WebClient service
Affected Products & Version Scope
Remediation & Live Workaround Commands
PATCH & WORKAROUND1. Official Patch & Version Upgrade Commands
Deploy the latest cumulative security updates from the Microsoft Update Catalog. To force a Windows Update check and installation via PowerShell, execute:
# Install and run Windows Update module to apply latest patches
Install-Module PSWindowsUpdate -Force -Verbose
Get-WindowsUpdate -AcceptAll -Install -AutoReboot2. Temporary Workaround & Hardening Configuration
If patching cannot be immediately scheduled, disable the Adobe Type Manager Font Driver (ATMFD) and disable the WebClient service to block remote WebDAV exploitation vectors.
# 1. Disable ATMFD via Registry
reg add 'HKLM\Software\Microsoft\Windows NT\CurrentVersion\Windows' /v DisableATMFD /t REG_DWORD /d 1 /f
# 2. Stop and Disable WebClient Service
Stop-Service -Name WebClient -Force
Set-Service -Name WebClient -StartupType Disabled3. Log Audit & IoC Verification Commands
Verify the status of the registry workaround and WebClient service using the following PowerShell script:
# Check ATMFD Registry Mitigation Status
$reg = Get-ItemProperty -Path 'HKLM:\Software\Microsoft\Windows NT\CurrentVersion\Windows' -Name DisableATMFD -ErrorAction SilentlyContinue
if ($reg -and $reg.DisableATMFD -eq 1) {
Write-Output 'SUCCESS: ATMFD is disabled.'
} else {
Write-Warning 'CRITICAL: ATMFD is enabled. System is vulnerable if unpatched.'
}
# Check WebClient Service Status
$svc = Get-Service -Name WebClient -ErrorAction SilentlyContinue
if ($svc.Status -eq 'Stopped' -or $svc -eq $null) {
Write-Output 'SUCCESS: WebClient service is stopped/disabled.'
} else {
Write-Warning 'CRITICAL: WebClient service is running.'
}Block Kernel Privilege Escalation & Ransomware Payloads Before You Can Reboot
Protect unpatched Windows, Linux, and macOS workloads against in-memory exploitation and lateral movement with autonomous EDR.
Technical Root Cause & Exploitation Mechanics
1. Vulnerability Overview & Root Cause
A critical remote code execution vulnerability exists in the Microsoft Windows Adobe Type Manager Library (ATMFD.dll). The root cause is an Out-of-bounds Write (CWE-787) vulnerability that occurs when the library improperly parses a specially crafted multi-master font in the Adobe Type 1 PostScript format. This improper input validation leads to system memory corruption.
2. Exploitation Mechanics & Attack Scenario
An attacker can exploit this vulnerability by convincing a user to open a specially crafted document or visit an untrusted web page containing malicious Type 1 PostScript fonts. Furthermore, the vulnerability can be triggered without user execution via the Windows Explorer Preview Pane when a user simply navigates to a directory containing the malicious font file. On systems prior to Windows 10, successful exploitation allows the attacker to execute arbitrary code in kernel mode.
3. Infrastructure & Business Impact
This vulnerability is listed in CISA's Known Exploited Vulnerabilities (KEV) catalog, indicating active exploitation in the wild. Successful exploitation grants full control of the target system to the attacker, posing severe risks of lateral movement, sensitive data exfiltration, and ransomware deployment across enterprise networks.
Official Vendor Advisories & References
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.
Frequently Asked SecOps Questions (CVE-2020-0938)
FAQQ1. How critical is CVE-2020-0938 and is it actively exploited in the wild?
CVE-2020-0938 is rated CVSS 7.8 (HIGH) with a 30-day EPSS exploitation probability of 69.0%. It is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, requiring immediate emergency remediation.
Q2. Which vendors and products are affected by CVE-2020-0938?
Primary impacted vendors include microsoft across windows, windows_server. Scope summary: Windows 7, Windows 8.1, Windows Server 2008, 2012, 2016, and 2019. (Windows 10 mitigates this by executing the font parser within an isolated AppContainer sandbox)
Q3. What temporary mitigations or workarounds exist for CVE-2020-0938 before patching?
[Mitigation] Apply official Microsoft security updates immediately, or implement workarounds including disabling ATMFD.dll and stopping the WebClient service Follow the CLI remediation commands and interactive SecOps checklist on this page to restrict exposure prior to your maintenance window.
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