CVE-2025-21346
📋 TL;DR
This CVE describes a security feature bypass vulnerability in Microsoft Office that could allow attackers to circumvent built-in security protections. It affects users running vulnerable versions of Microsoft Office applications. Successful exploitation could lead to unauthorized actions or code execution.
💻 Affected Systems
- Microsoft Office
- Microsoft 365 Apps
📦 What is this software?
365 Apps by Microsoft
365 Apps by Microsoft
Office by Microsoft
Office 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
Complete bypass of Office security features leading to arbitrary code execution with user privileges, potentially enabling malware installation or data theft.
Likely Case
Limited bypass of specific security controls allowing malicious macros or scripts to run despite security settings, leading to credential theft or limited system compromise.
If Mitigated
Attack fails due to layered security controls, macro blocking policies, or application hardening.
🎯 Exploit Status
Requires user interaction (opening malicious document) and may require social engineering. No public exploit code known at this time.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Latest security updates from Microsoft (check specific KB numbers in advisory)
Vendor Advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-21346
Restart Required: No
Instructions:
1. Open any Office application. 2. Go to File > Account > Update Options > Update Now. 3. For enterprise deployments, deploy latest Office security updates via WSUS, SCCM, or Intune.
🔧 Temporary Workarounds
Disable Macros
WindowsConfigure Office to block macros from running, especially from untrusted sources.
Set Group Policy: Computer Configuration > Administrative Templates > Microsoft Office 2016 > Security Settings > Macro Security > Set macro security to 'Disable all macros without notification'
Enable Protected View
WindowsEnsure Protected View is enabled for files from the internet.
Set Group Policy: Computer Configuration > Administrative Templates > Microsoft Office 2016 > Security Settings > Protected View > Enable all Protected View settings
🧯 If You Can't Patch
- Implement application whitelisting to block unauthorized Office processes
- Deploy email filtering to block malicious attachments and enable macro scanning
🔍 How to Verify
Check if Vulnerable:
Check Office version against patched versions in Microsoft advisory. Vulnerable if running unpatched affected versions.Check Version:
In Word/Excel/PowerPoint: File > Account > About [Application] shows version numberVerify Fix Applied:
Verify Office version matches or exceeds patched version listed in Microsoft advisory. Check that security updates are installed.📡 Detection & Monitoring
Log Indicators:
- Office application crashes with unusual error codes
- Security feature override events in Windows Event Log
- Macro execution from untrusted locations
Network Indicators:
- Unusual outbound connections from Office processes
- Downloads of suspicious files by Office applications
SIEM Query:
EventID=1 OR EventID=4688 | where ProcessName contains "WINWORD.EXE" or ProcessName contains "EXCEL.EXE" or ProcessName contains "POWERPNT.EXE" | where CommandLine contains suspicious patterns