CVE-2019-1149
📋 TL;DR
This CVE describes a remote code execution vulnerability in Windows font library that allows attackers to execute arbitrary code by tricking users into viewing malicious embedded fonts. All Windows systems with vulnerable font library components are affected. The vulnerability can be exploited through web pages or document files containing specially crafted fonts.
💻 Affected Systems
- Microsoft Windows
📦 What is this software?
Office by Microsoft
Windows 10 by Microsoft
Windows 10 by Microsoft
Windows 10 by Microsoft
Windows 10 by Microsoft
Windows 10 by Microsoft
Windows 10 by Microsoft
Windows 10 by Microsoft
Windows 7 by Microsoft
Windows 8.1 by Microsoft
Windows Rt 8.1 by Microsoft
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with administrative privileges, allowing installation of malware, data theft, and persistent backdoor access.
Likely Case
Targeted attacks against users opening malicious documents or visiting compromised websites, leading to initial foothold for further exploitation.
If Mitigated
Limited impact with proper user training, application whitelisting, and network segmentation preventing lateral movement.
🎯 Exploit Status
Exploitation requires user interaction (opening document or visiting website). Public proof-of-concept exists showing heap corruption in font subsetting DLL.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: July 2019 security updates (KB4507453 for Windows 10 1903, KB4507469 for Windows Server 2019, etc.)
Vendor Advisory: https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2019-1149
Restart Required: Yes
Instructions:
1. Apply July 2019 Windows security updates via Windows Update. 2. For enterprise: Deploy through WSUS or SCCM. 3. Verify installation in Windows Update history. 4. Restart systems as required.
🔧 Temporary Workarounds
Disable font embedding in Office documents
windowsPrevents exploitation through Office documents by disabling embedded font processing
Set registry key: HKCU\Software\Microsoft\Office\16.0\Common\Security\FontEmbedding to 0
Use EMET or Windows Defender Exploit Guard
windowsEnable exploit protection features to mitigate memory corruption attacks
Enable Attack Surface Reduction rules in Windows Defender
🧯 If You Can't Patch
- Implement application whitelisting to prevent unauthorized code execution
- Use network segmentation to isolate vulnerable systems and restrict internet access
🔍 How to Verify
Check if Vulnerable:
Check Windows version and compare with patched versions. Systems without July 2019 updates are vulnerable.Check Version:
wmic os get caption, version, buildnumberVerify Fix Applied:
Verify KB4507453 (or equivalent for your version) is installed in Windows Update history.📡 Detection & Monitoring
Log Indicators:
- Windows Event Logs showing font library crashes (Event ID 1000)
- Process creation from font-related processes
Network Indicators:
- HTTP requests to suspicious domains hosting font files
- Unusual outbound connections after document opening
SIEM Query:
EventID=1000 AND SourceName="Application Error" AND ProcessName LIKE "%font%"🔗 References
- http://packetstormsecurity.com/files/154086/Microsoft-Font-Subsetting-DLL-FixSbitSubTables-Heap-Corruption.html
- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2019-1149
- http://packetstormsecurity.com/files/154086/Microsoft-Font-Subsetting-DLL-FixSbitSubTables-Heap-Corruption.html
- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2019-1149
