CVE-2025-27749
📋 TL;DR
A use-after-free 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 on Windows systems.
💻 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 same privileges as the logged-in user, potentially leading to data theft, ransomware deployment, or lateral movement within the network.
Likely Case
Local privilege escalation leading to unauthorized access to sensitive documents, credential theft, or installation of persistent malware.
If Mitigated
Limited impact with proper application sandboxing and user privilege restrictions, potentially only crashing the Office application.
🎯 Exploit Status
Exploitation requires social engineering to deliver malicious document. No known active exploitation at time of disclosure.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: April 2025 security update (KB503XXXX)
Vendor Advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-27749
Restart Required: Yes
Instructions:
1. Open any Office application. 2. Go to File > Account > Update Options > Update Now. 3. Restart computer after update completes. For enterprise deployments, deploy via Microsoft Update or WSUS.
🔧 Temporary Workarounds
Disable Office macro execution
windowsPrevents execution of malicious macros that could trigger the vulnerability
Set GPO: Computer Configuration > Administrative Templates > Microsoft Office 2016 > Security Settings > Trust Center > Block macros from running in Office files from the Internet
Enable Protected View for all documents
windowsForces all documents to open in sandboxed Protected View mode
Set registry key: HKCU\Software\Microsoft\Office\16.0\Word\Security\ProtectedView = 1
🧯 If You Can't Patch
- Implement application whitelisting to block unauthorized Office document execution
- Deploy endpoint detection and response (EDR) solutions to monitor for suspicious Office process behavior
🔍 How to Verify
Check if Vulnerable:
Check Office version in any Office app via File > Account > About. If version is earlier than April 2025 update, system is vulnerable.Check Version:
wmic product where "name like 'Microsoft Office%'" get versionVerify Fix Applied:
Verify KB503XXXX is installed via Control Panel > Programs > Programs and Features > View installed updates📡 Detection & Monitoring
Log Indicators:
- Office application crashes with memory access violations
- Suspicious child processes spawned from Office applications
Network Indicators:
- Unexpected outbound connections from Office processes
- DNS queries for known exploit domains
SIEM Query:
EventID=1000 OR EventID=1001 AND SourceName="Application Error" AND ProcessName="WINWORD.EXE" OR "EXCEL.EXE" OR "POWERPNT.EXE"