CVE-2025-30393
📋 TL;DR
This vulnerability is a use-after-free memory corruption flaw in Microsoft Office Excel that allows an attacker to execute arbitrary code on a victim's system by tricking them into opening a malicious Excel file. It affects users running vulnerable versions of Microsoft Excel. Successful exploitation requires user interaction to open a specially crafted document.
💻 Affected Systems
- Microsoft Excel
📦 What is this software?
365 Apps 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
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 code execution with the privileges of the current user, potentially leading to data exfiltration, credential harvesting, or installation of persistent malware.
If Mitigated
Limited impact if macros are disabled, files are opened in Protected View, or the user has limited privileges, though memory corruption could still cause application crashes.
🎯 Exploit Status
Exploitation requires user interaction (opening a file) and likely involves crafting a malicious Excel document; no public exploit code is known at this time.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check Microsoft Security Update Guide for specific version numbers; apply latest security updates for Microsoft Office/Excel.
Vendor Advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-30393
Restart Required: Yes
Instructions:
1. Open Microsoft Excel. 2. Go to File > Account > Update Options > Update Now. 3. Alternatively, use Windows Update for system-wide Office updates. 4. Restart the system if prompted.
🔧 Temporary Workarounds
Disable automatic opening of Excel files
windowsConfigure Excel to open files in Protected View or disable automatic opening from email/websites.
In Excel: File > Options > Trust Center > Trust Center Settings > Protected View > Enable all options
Block suspicious file extensions
allPrevent delivery of potentially malicious Excel files via email.
🧯 If You Can't Patch
- Restrict user privileges to limit impact of code execution (e.g., run Excel with standard user accounts, not administrator).
- Implement application whitelisting to prevent unauthorized executables from running post-exploitation.
🔍 How to Verify
Check if Vulnerable:
Check Excel version via File > Account > About Excel; compare with patched versions listed in Microsoft advisory.Check Version:
In Excel: File > Account > About Excel (Windows) or Excel > About Excel (macOS)Verify Fix Applied:
Verify Excel version matches or exceeds the patched version; ensure Windows Update shows no pending Office security updates.📡 Detection & Monitoring
Log Indicators:
- Windows Event Logs: Application crashes of EXCEL.EXE with memory access violations
- Antivirus logs: Detection of malicious Excel files or exploit attempts
Network Indicators:
- Unusual outbound connections from Excel process post-file opening
- Downloads of Excel files from suspicious sources
SIEM Query:
EventID=1000 OR EventID=1001 AND ProcessName="EXCEL.EXE" AND (ExceptionCode=0xc0000005 OR ExceptionCode=0xc0000409)