CVE-2025-59240
📋 TL;DR
This vulnerability in Microsoft Office Excel allows an unauthorized local attacker to access sensitive information from Excel files. It affects users running vulnerable versions of Excel who open malicious or specially crafted documents. The attacker must have local access to the target system.
💻 Affected Systems
- Microsoft Office Excel
📦 What is this software?
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 →
⚠️ Risk & Real-World Impact
Worst Case
An attacker with local access could extract confidential data, credentials, or proprietary information from Excel files stored on the system.
Likely Case
Information disclosure of data within Excel files to unauthorized local users or malware with local execution privileges.
If Mitigated
Limited impact with proper access controls, file permissions, and user awareness about opening untrusted documents.
🎯 Exploit Status
Exploitation requires local access and user interaction (opening malicious file). No public exploit details available at this time.
🛠️ 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-2025-59240
Restart Required: Yes
Instructions:
1. Open Excel and go to File > Account > Update Options > Update Now. 2. Alternatively, use Windows Update for Microsoft 365/Office updates. 3. Apply latest security patches from Microsoft Update Catalog if using standalone Office.
🔧 Temporary Workarounds
Restrict Excel file execution
windowsConfigure Group Policy or local security settings to block Excel from opening files from untrusted locations.
Use Protected View
windowsEnsure Protected View is enabled for files from the internet in Excel Trust Center settings.
🧯 If You Can't Patch
- Implement strict file access controls and permissions to limit who can open Excel files.
- Educate users to never open Excel files from untrusted sources and to use Protected View for external files.
🔍 How to Verify
Check if Vulnerable:
Check Excel version via File > Account > About Excel. Compare with patched versions in Microsoft advisory.Check Version:
In Excel: File > Account > About Excel (Windows) or Excel > About Excel (macOS)Verify Fix Applied:
Verify Excel has updated to latest version and check that security update KB number from Microsoft advisory is installed.📡 Detection & Monitoring
Log Indicators:
- Windows Event Logs showing Excel crashes or unusual file access patterns
- Office telemetry logs indicating file parsing errors
Network Indicators:
- Not applicable - local vulnerability
SIEM Query:
EventID=1000 OR EventID=1001 Source='Microsoft Office' AND ProcessName='EXCEL.EXE' AND Keywords contains 'Error'