CVE-2025-54900
📋 TL;DR
A heap-based buffer overflow vulnerability in Microsoft Office Excel allows attackers to execute arbitrary code on affected systems by tricking users into opening malicious Excel files. 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
Complete system compromise with attacker gaining full control of the victim's computer, enabling data theft, ransomware deployment, or lateral movement within the network.
Likely Case
Local privilege escalation leading to data exfiltration, installation of backdoors, or credential harvesting from the compromised system.
If Mitigated
Limited impact with proper application sandboxing and user privilege restrictions preventing full system compromise.
🎯 Exploit Status
Exploitation requires user interaction to open malicious file. 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-2025-54900
Restart Required: Yes
Instructions:
1. Open Microsoft Excel. 2. Go to File > Account > Update Options > Update Now. 3. Restart Excel when prompted. 4. Alternatively, apply Windows Update patches through Windows Update settings.
🔧 Temporary Workarounds
Disable Excel file opening
windowsPrevent Excel from opening potentially malicious files by modifying file associations
assoc .xlsx=
assoc .xls=
assoc .xlsm=
Enable Protected View
windowsForce all Excel files to open in Protected View to prevent automatic code execution
Excel Options > Trust Center > Trust Center Settings > Protected View > Enable all Protected View options
🧯 If You Can't Patch
- Implement application whitelisting to block unauthorized Excel execution
- Restrict user privileges to standard user accounts (no admin rights)
🔍 How to Verify
Check if Vulnerable:
Check Excel version via File > Account > About Excel and compare against patched versions in Microsoft advisoryCheck Version:
wmic product where name="Microsoft Office Excel" get versionVerify Fix Applied:
Verify Excel has updated to latest version and attempt to reproduce with test files if available📡 Detection & Monitoring
Log Indicators:
- Excel crash logs with heap corruption errors
- Windows Event Logs showing Excel process spawning unexpected child processes
Network Indicators:
- Outbound connections from Excel process to unknown external IPs
- DNS queries for suspicious domains from Excel process
SIEM Query:
process_name="EXCEL.EXE" AND (event_id=1000 OR event_id=1001) AND message CONTAINS "heap"