CVE-2025-53739
📋 TL;DR
A type confusion vulnerability in Microsoft Office Excel allows attackers to execute arbitrary code on a victim's system by tricking them into opening a malicious Excel file. This affects all users running vulnerable versions of Microsoft Excel. The attacker needs to deliver the malicious file through email, downloads, or other means.
💻 Affected Systems
- Microsoft Excel
📦 What is this software?
365 Apps by Microsoft
365 Apps by Microsoft
Excel by Microsoft
Excel 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
Full system compromise with attacker gaining complete control over the victim's computer, installing malware, stealing data, and moving laterally within the network.
Likely Case
Local code execution leading to data theft, ransomware deployment, or credential harvesting from the compromised system.
If Mitigated
Limited impact with proper application sandboxing and least privilege controls preventing system-wide compromise.
🎯 Exploit Status
Requires social engineering to deliver malicious Excel file. Type confusion vulnerabilities often lead to reliable exploitation once weaponized.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check Microsoft's monthly security updates for Office/Excel patches
Vendor Advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-53739
Restart Required: Yes
Instructions:
1. Open any Office application. 2. Go to File > Account > Update Options > Update Now. 3. Alternatively, use Windows Update for Microsoft 365 apps. 4. Restart system after update.
🔧 Temporary Workarounds
Block Excel file execution via Group Policy
windowsPrevent Excel from opening files from untrusted locations using Application Control policies
Configure via Windows Group Policy: Computer Configuration > Policies > Windows Settings > Security Settings > Application Control Policies
Use Protected View for all Excel files
windowsForce Excel to open all files in Protected View to prevent automatic code execution
Set registry key: HKCU\Software\Microsoft\Office\16.0\Excel\Security\ProtectedView with value 1
🧯 If You Can't Patch
- Implement application whitelisting to block unauthorized Excel execution
- Use email filtering to block Excel attachments and educate users about phishing risks
🔍 How to Verify
Check if Vulnerable:
Check Excel version via File > Account > About Excel and compare with Microsoft's patched version listCheck Version:
In Excel: File > Account > About Excel shows version numberVerify Fix Applied:
Verify Office updates are installed via Control Panel > Programs > Programs and Features > View installed updates📡 Detection & Monitoring
Log Indicators:
- Excel crash logs with memory access violations
- Windows Event Logs showing Excel spawning unusual child processes
Network Indicators:
- Excel making unexpected outbound connections after opening files
- DNS requests to suspicious domains from Excel process
SIEM Query:
source="windows" AND (process_name="EXCEL.EXE" AND (event_id=1000 OR child_process!=""))