CVE-2025-21345
📋 TL;DR
This vulnerability in Microsoft Office Visio allows attackers to execute arbitrary code by tricking users into opening specially crafted files. It affects all users running vulnerable versions of Visio who open malicious documents. The vulnerability stems from a use-after-free memory corruption issue.
💻 Affected Systems
- Microsoft Office Visio
📦 What is this software?
365 Apps by Microsoft
365 Apps 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 system compromise with attacker gaining full control of the victim's computer, data theft, ransomware deployment, and lateral movement within the network.
Likely Case
Local privilege escalation leading to data exfiltration, malware installation, and persistence mechanisms being established on the compromised system.
If Mitigated
Limited impact with only application crash or denial of service if proper application sandboxing and exploit mitigations are in place.
🎯 Exploit Status
Exploitation requires user interaction to open malicious file. Memory corruption vulnerability (CWE-416) typically requires bypassing modern exploit mitigations like ASLR and DEP.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: February 2025 security update for Microsoft Office
Vendor Advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-21345
Restart Required: No
Instructions:
1. Open any Office application. 2. Go to File > Account > Update Options > Update Now. 3. Alternatively, download and install the security update from Microsoft Update Catalog. 4. Ensure Windows Update is configured to receive Office updates.
🔧 Temporary Workarounds
Block Visio file extensions
allPrevent opening of Visio files via email attachments or network shares
Use Group Policy or endpoint protection to block .vsd, .vsdx, .vss, .vssx, .vst, .vstx file extensions
Enable Protected View
allForce all Visio files from internet or untrusted locations to open in Protected View
In Visio: File > Options > Trust Center > Trust Center Settings > Protected View > Check all three options
🧯 If You Can't Patch
- Implement application whitelisting to prevent unauthorized Visio execution
- Deploy enhanced email filtering to block malicious Visio attachments
- Educate users about the risks of opening Visio files from untrusted sources
- Use Microsoft Defender Application Guard for Office if available
🔍 How to Verify
Check if Vulnerable:
Check Visio version via File > Account > About Visio. If version is older than February 2025 update, system is vulnerable.Check Version:
In Visio: File > Account > About Visio, or PowerShell: Get-ItemProperty "HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\*" | Where-Object {$_.DisplayName -like "*Visio*"} | Select-Object DisplayName, DisplayVersionVerify Fix Applied:
Verify Visio version shows February 2025 or later update installed. Check Windows Update history for Office security updates.📡 Detection & Monitoring
Log Indicators:
- Windows Event Logs: Application crashes of VISIO.EXE with exception codes like 0xC0000005 (ACCESS_VIOLATION)
- Microsoft Defender for Endpoint alerts for suspicious Office process behavior
- Process creation from Visio with unusual command line arguments
Network Indicators:
- Outbound connections from Visio process to suspicious IPs
- DNS queries for known malicious domains from Office processes
- Unusual SMB or HTTP traffic originating from Visio
SIEM Query:
source="windows" AND (process_name="VISIO.EXE" AND (event_id=1000 OR event_id=1001)) OR (parent_process="VISIO.EXE" AND process_execution="powershell.exe" OR "cmd.exe")