CVE-2023-24953
📋 TL;DR
CVE-2023-24953 is a use-after-free vulnerability in Microsoft Excel that allows remote code execution when a user opens a specially crafted malicious Excel file. Attackers can exploit this to execute arbitrary code with the privileges of the current user. This affects users running vulnerable versions of Microsoft Excel on Windows systems.
💻 Affected Systems
- Microsoft Excel
📦 What is this software?
365 Apps by Microsoft
Excel 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 →
⚠️ 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
Malware installation leading to data exfiltration, credential theft, or system disruption for individual users who open malicious Excel files.
If Mitigated
Limited impact with proper email filtering, user awareness training, and application sandboxing preventing successful exploitation.
🎯 Exploit Status
Requires user interaction to open malicious Excel file. No publicly available exploit code as of analysis.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Security updates released in May 2023
Vendor Advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2023-24953
Restart Required: Yes
Instructions:
1. Open Microsoft Excel. 2. Go to File > Account > Update Options > Update Now. 3. Alternatively, use Windows Update for Office updates. 4. Restart computer after installation.
🔧 Temporary Workarounds
Block Excel file types via email filtering
allConfigure email gateways to block or quarantine Excel files (.xls, .xlsx, .xlsm) from untrusted sources
Enable Protected View
windowsEnsure Protected View is enabled in Excel to open files from potentially unsafe locations in read-only mode
🧯 If You Can't Patch
- Implement application whitelisting to prevent unauthorized Excel execution
- Deploy Microsoft Office security hardening guidelines and disable macros
🔍 How to Verify
Check if Vulnerable:
Check Excel version via File > Account > About Excel. Compare against patched versions from Microsoft advisory.Check Version:
In Excel: File > Account > About ExcelVerify Fix Applied:
Verify Windows Update history shows May 2023 Office security updates installed, or check Excel version matches patched versions.📡 Detection & Monitoring
Log Indicators:
- Windows Event Logs showing Excel crashes, suspicious child processes spawned from Excel.exe
Network Indicators:
- Unusual outbound connections from Excel process, especially to known malicious IPs
SIEM Query:
Process Creation where ParentImage contains 'excel.exe' AND (CommandLine contains suspicious patterns OR Image contains unusual executables)