CVE-2025-29820
📋 TL;DR
A use-after-free vulnerability in Microsoft Office Word allows attackers to execute arbitrary code on vulnerable systems by tricking users into opening malicious documents. This affects all users running unpatched versions of Microsoft Word. Successful exploitation requires user interaction but can lead to full system compromise.
💻 Affected Systems
- Microsoft Office Word
📦 What is this software?
365 Apps by Microsoft
365 Apps by Microsoft
Office by Microsoft
Office by Microsoft
Office by Microsoft
Office by Microsoft
Office Long Term Servicing Channel by Microsoft
View all CVEs affecting Office Long Term Servicing Channel →
Office Long Term Servicing Channel by Microsoft
View all CVEs affecting Office Long Term Servicing Channel →
Office Long Term Servicing Channel by Microsoft
View all CVEs affecting Office Long Term Servicing Channel →
Office Long Term Servicing Channel by Microsoft
View all CVEs affecting Office Long Term Servicing Channel →
Office Long Term Servicing Channel by Microsoft
View all CVEs affecting Office Long Term Servicing Channel →
⚠️ 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
Local code execution leading to malware installation, credential harvesting, or lateral movement within the network.
If Mitigated
Limited impact with proper application sandboxing, restricted user privileges, and macro security settings preventing successful exploitation.
🎯 Exploit Status
Exploitation requires user interaction (opening malicious document). No public exploit code available at this time.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check Microsoft Security Update Guide for specific patch versions
Vendor Advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-29820
Restart Required: Yes
Instructions:
1. Open Microsoft Word
2. Go to File > Account > Update Options
3. Select 'Update Now'
4. Restart Word when prompted
5. Verify update in File > Account > About Word
🔧 Temporary Workarounds
Disable automatic document opening
windowsPrevent Word from automatically opening documents from untrusted sources
Set registry key: HKCU\Software\Microsoft\Office\16.0\Word\Security\FileValidation = 1
Enable Protected View
windowsForce all documents from internet sources to open in Protected View
Set registry key: HKCU\Software\Microsoft\Office\16.0\Word\Security\ProtectedView = 1
🧯 If You Can't Patch
- Implement application whitelisting to block unauthorized Word documents
- Deploy Microsoft Attack Surface Reduction rules to block Office macro threats
🔍 How to Verify
Check if Vulnerable:
Check Word version against Microsoft Security Update Guide for CVE-2025-29820Check Version:
In Word: File > Account > About WordVerify Fix Applied:
Verify Word version is updated to patched version listed in Microsoft advisory📡 Detection & Monitoring
Log Indicators:
- Word crash logs with memory access violations
- Windows Event Logs showing Word process spawning unexpected child processes
Network Indicators:
- Unusual outbound connections from Word process
- DNS requests to suspicious domains after document opening
SIEM Query:
EventID=1 AND ParentImage LIKE '%WINWORD.EXE%' AND Image NOT LIKE '%OFFICE%'