CVE-2025-49711
📋 TL;DR
A use-after-free 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 on Windows systems.
💻 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 the same privileges as the logged-in user, potentially leading to 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 if user runs with minimal privileges, has application control policies, and doesn't open untrusted files.
🎯 Exploit Status
Requires user to open malicious Excel file. Use-after-free vulnerabilities typically require careful memory manipulation.
🛠️ 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-2025-49711
Restart Required: Yes
Instructions:
1. Open Excel and go to File > Account
2. Click Update Options > Update Now
3. Alternatively, use Windows Update: Settings > Update & Security > Windows Update > Check for updates
4. Install all available Office updates
5. Restart computer if prompted
🔧 Temporary Workarounds
Disable Excel file opening
windowsTemporarily block Excel files from untrusted sources
reg add "HKCU\Software\Microsoft\Office\16.0\Excel\Security" /v "FileValidation" /t REG_DWORD /d 3 /f
Use Protected View
windowsForce all Excel files to open in Protected View
reg add "HKCU\Software\Microsoft\Office\16.0\Excel\Security\ProtectedView" /v "DisableInternetFilesInPV" /t REG_DWORD /d 0 /f
reg add "HKCU\Software\Microsoft\Office\16.0\Excel\Security\ProtectedView" /v "DisableAttachmentsInPV" /t REG_DWORD /d 0 /f
🧯 If You Can't Patch
- Implement application control policies to block Excel execution from untrusted locations
- Use email filtering to block Excel attachments and educate users about phishing risks
🔍 How to Verify
Check if Vulnerable:
Check Excel version: File > Account > About Excel. Compare with patched versions in Microsoft advisory.Check Version:
powershell "Get-ItemProperty 'HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\*' | Where-Object {$_.DisplayName -like '*Excel*'} | Select-Object DisplayName, DisplayVersion"Verify Fix Applied:
Verify Office updates are installed: Control Panel > Programs > Programs and Features > Microsoft Office > Change > Online Repair📡 Detection & Monitoring
Log Indicators:
- Excel crash logs with memory access violations
- Windows Event Logs: Application crashes with Excel.exe
- Process creation from Excel with unusual parent-child relationships
Network Indicators:
- Excel making unexpected network connections after file open
- DNS requests to suspicious domains following Excel execution
SIEM Query:
source="*windows*" (process_name="excel.exe" AND (event_id=1000 OR event_id=1001)) OR (parent_process="excel.exe" AND process_name NOT IN ("explorer.exe", "svchost.exe"))