CVE-2020-1576
📋 TL;DR
This is a remote code execution vulnerability in Microsoft SharePoint that allows attackers to run arbitrary code by uploading specially crafted application packages. It affects SharePoint servers where users can upload packages, potentially compromising the entire SharePoint farm and application pool.
💻 Affected Systems
- Microsoft SharePoint Server
- Microsoft SharePoint Foundation
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of SharePoint server farm, data exfiltration, lateral movement to other systems, and persistent backdoor installation.
Likely Case
Unauthorized code execution leading to data theft, privilege escalation, and SharePoint environment manipulation.
If Mitigated
Limited impact with proper upload restrictions and network segmentation, potentially only affecting isolated SharePoint components.
🎯 Exploit Status
Requires authenticated user with package upload permissions. Exploitation involves crafting malicious SharePoint application packages.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Refer to Microsoft Security Update for specific KB numbers
Vendor Advisory: https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2020-1576
Restart Required: Yes
Instructions:
1. Download appropriate security update from Microsoft Update Catalog. 2. Apply update to all SharePoint servers. 3. Restart SharePoint services. 4. Test functionality.
🔧 Temporary Workarounds
Restrict SharePoint Application Package Uploads
windowsTemporarily disable or restrict upload of SharePoint application packages (.app files) through SharePoint Central Administration or PowerShell.
Set-SPAppAcquisitionConfiguration -EnableAppAcquisition $false
Implement Upload Validation
windowsAdd additional validation layers for uploaded packages using SharePoint event receivers or third-party security tools.
🧯 If You Can't Patch
- Implement strict access controls on SharePoint upload functionality
- Deploy network segmentation and monitor for suspicious upload activities
🔍 How to Verify
Check if Vulnerable:
Check SharePoint version and compare with Microsoft's affected versions list. Review if application package uploads are enabled.Check Version:
Get-SPFarm | Select BuildVersionVerify Fix Applied:
Verify security update is installed via Control Panel > Programs and Features > View installed updates, and test package upload functionality.📡 Detection & Monitoring
Log Indicators:
- Unusual SharePoint application package uploads
- Failed package validation events in SharePoint logs
- Unexpected process execution from SharePoint worker processes
Network Indicators:
- Unusual outbound connections from SharePoint servers
- Large file uploads to SharePoint application endpoints
SIEM Query:
source="SharePoint" AND (event_id="6398" OR event_id="6399") AND message="*package*"