CVE-2021-1715
📋 TL;DR
CVE-2021-1715 is a remote code execution vulnerability in Microsoft Word that allows attackers to execute arbitrary code by tricking users into opening specially crafted documents. This affects users of Microsoft Word on Windows systems. Successful exploitation requires user interaction but can lead to full system compromise.
💻 Affected Systems
- Microsoft Word
- Microsoft Office
📦 What is this software?
365 Apps by Microsoft
Office by Microsoft
Office by Microsoft
Office by Microsoft
Office Web Apps by Microsoft
Word by Microsoft
Word by Microsoft
Word by Microsoft
Word by Microsoft
⚠️ Risk & Real-World Impact
Worst Case
Complete system takeover with attacker gaining the same privileges as the logged-in user, enabling data theft, ransomware deployment, or persistent backdoor installation.
Likely Case
Malware installation leading to data exfiltration, credential theft, or lateral movement within the network.
If Mitigated
Limited impact due to application sandboxing, least privilege accounts, and macro restrictions preventing code execution.
🎯 Exploit Status
Exploitation requires user interaction to open a malicious document. Proof-of-concept code has been publicly released.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Security updates released in January 2021 (e.g., KB4589198 for Office 2019)
Vendor Advisory: https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-1715
Restart Required: Yes
Instructions:
1. Open Microsoft Word. 2. Go to File > Account > Update Options > Update Now. 3. Alternatively, use Windows Update or Microsoft Update to install the latest security updates. 4. Restart affected systems after patching.
🔧 Temporary Workarounds
Block Office macros from the internet
windowsPrevents Office files downloaded from the internet from running macros, which could be used in exploitation chains.
Set-ItemProperty -Path "HKLM:\SOFTWARE\Policies\Microsoft\Office\16.0\Word\Security" -Name "BlockInternetMacros" -Value 1 -Type DWord
Use Microsoft Office Viewer
windowsOpen suspicious documents in Microsoft Office Viewer instead of full Word application to prevent code execution.
🧯 If You Can't Patch
- Implement application whitelisting to prevent unauthorized executables from running
- Use email filtering to block suspicious Office attachments and enable macro blocking policies
🔍 How to Verify
Check if Vulnerable:
Check Office version in Word via File > Account > About Word. Compare against patched versions listed in Microsoft advisory.Check Version:
wmic product where "name like 'Microsoft Office%'" get versionVerify Fix Applied:
Verify security update KB4589198 or later is installed via Control Panel > Programs > Programs and Features > View installed updates.📡 Detection & Monitoring
Log Indicators:
- Windows Event Logs showing Word crashes with suspicious parameters
- Process creation events showing unexpected child processes from WINWORD.EXE
Network Indicators:
- Outbound connections from Word process to suspicious IPs
- DNS queries for command and control domains
SIEM Query:
EventID=1 AND ParentImage="*\WINWORD.EXE" AND (CommandLine="*powershell*" OR CommandLine="*cmd*")