CVE-2025-29791
📋 TL;DR
A type confusion vulnerability in Microsoft Office 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 Office. The attacker must deliver a malicious file to the target.
💻 Affected Systems
- Microsoft Office
- Microsoft 365 Apps
📦 What is this software?
365 Apps 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 →
⚠️ Risk & Real-World Impact
Worst Case
Full system compromise with attacker gaining complete control over the victim's computer, enabling data theft, ransomware deployment, or persistent backdoor installation.
Likely Case
Local code execution leading to malware installation, credential theft, or lateral movement within the network.
If Mitigated
Limited impact with proper application sandboxing, macro restrictions, and user awareness preventing malicious file execution.
🎯 Exploit Status
Requires social engineering to deliver malicious file. No public exploit code known at this time.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check Microsoft Update for latest security updates
Vendor Advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-29791
Restart Required: Yes
Instructions:
1. Open any Office application. 2. Go to File > Account > Update Options > Update Now. 3. Restart computer after update completes. 4. Verify update through File > Account > About [Application].
🔧 Temporary Workarounds
Disable Office macro execution
windowsPrevents Office documents from running potentially malicious macros
Set Group Policy: Computer Configuration > Administrative Templates > Microsoft Office 2016 > Security Settings > Trust Center > Block macros from running in Office files from the Internet
Use Office Viewer mode
allOpen suspicious documents in Protected View/Read-Only mode
🧯 If You Can't Patch
- Implement application whitelisting to block unauthorized Office document execution
- Deploy email filtering to block Office attachments from untrusted sources
🔍 How to Verify
Check if Vulnerable:
Check Office version against patched versions in Microsoft advisory. Unpatched versions are vulnerable.Check Version:
In Word/Excel/PowerPoint: File > Account > About [Application]Verify Fix Applied:
Verify Office applications show updated version numbers after patch installation📡 Detection & Monitoring
Log Indicators:
- Office application crashes with unusual error codes
- Process creation from Office applications (winword.exe, excel.exe)
Network Indicators:
- Outbound connections from Office processes to suspicious IPs
SIEM Query:
Process creation where parent_process contains 'winword.exe' or 'excel.exe' or 'powerpnt.exe'