CVE-2025-47166
📋 TL;DR
CVE-2025-47166 is a deserialization vulnerability in Microsoft Office SharePoint that allows authenticated attackers to execute arbitrary code remotely. This affects organizations using vulnerable SharePoint versions, potentially compromising entire SharePoint environments and connected systems.
💻 Affected Systems
- Microsoft Office SharePoint Server
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of SharePoint servers leading to domain takeover, data exfiltration, ransomware deployment, and lateral movement across the network.
Likely Case
Unauthorized code execution on SharePoint servers resulting in data theft, service disruption, and installation of backdoors for persistent access.
If Mitigated
Limited impact with proper network segmentation, application controls, and monitoring detecting exploitation attempts before successful compromise.
🎯 Exploit Status
Requires authenticated access but deserialization vulnerabilities often have reliable exploitation paths once understood.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: To be specified in Microsoft's security update
Vendor Advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-47166
Restart Required: Yes
Instructions:
1. Review Microsoft's security advisory for CVE-2025-47166
2. Apply the latest security update for SharePoint Server
3. Restart SharePoint services and verify functionality
🔧 Temporary Workarounds
Restrict SharePoint Access
allLimit network access to SharePoint servers to only trusted users and systems
Implement Application Control
windowsUse Windows Defender Application Control or similar to restrict code execution on SharePoint servers
🧯 If You Can't Patch
- Implement strict network segmentation to isolate SharePoint servers from critical systems
- Enhance monitoring and alerting for suspicious deserialization activity and code execution attempts
🔍 How to Verify
Check if Vulnerable:
Check SharePoint Server version against Microsoft's security advisory for affected versionsCheck Version:
Get-SPFarm | Select BuildVersion (PowerShell on SharePoint server)Verify Fix Applied:
Verify SharePoint Server has been updated to the patched version specified in Microsoft's advisory📡 Detection & Monitoring
Log Indicators:
- Unusual deserialization events in SharePoint logs
- Unexpected process creation on SharePoint servers
- Authentication from unusual locations or accounts followed by code execution
Network Indicators:
- Unusual outbound connections from SharePoint servers
- Suspicious PowerShell or command execution traffic
SIEM Query:
source="sharepoint_logs" AND ("deserialization" OR "ObjectDataProvider" OR "LosFormatter")