CVE-2020-16953
📋 TL;DR
This CVE describes an information disclosure vulnerability in Microsoft SharePoint Server where improper memory handling allows authenticated attackers to access sensitive information. The vulnerability requires an attacker to have valid login credentials and run a specially crafted application on the affected system. Organizations using vulnerable SharePoint Server versions are affected.
💻 Affected Systems
- Microsoft SharePoint Server
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
An authenticated attacker could access sensitive SharePoint data, potentially including confidential documents, user information, or system configuration details, leading to further system compromise or data exfiltration.
Likely Case
An authenticated malicious insider or compromised account could access sensitive SharePoint content they shouldn't have permission to view, potentially exposing confidential business information.
If Mitigated
With proper access controls, network segmentation, and monitoring, the impact is limited to authorized users accessing data they shouldn't see, which can be detected through audit logs.
🎯 Exploit Status
Exploitation requires authenticated access and ability to run specially crafted applications on the SharePoint server
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Specific patch version available through Microsoft Security Update
Vendor Advisory: https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2020-16953
Restart Required: Yes
Instructions:
1. Apply Microsoft's security update for SharePoint Server. 2. Restart affected SharePoint services or server. 3. Verify patch installation through Windows Update history or SharePoint version check.
🔧 Temporary Workarounds
Restrict User Access
allLimit SharePoint server access to only necessary administrative users and implement least privilege principles
Application Control
windowsImplement application whitelisting to prevent execution of unauthorized applications on SharePoint servers
🧯 If You Can't Patch
- Implement strict access controls and monitor for unusual authenticated user activity
- Segment SharePoint servers from other critical systems to limit lateral movement potential
🔍 How to Verify
Check if Vulnerable:
Check SharePoint Server version against Microsoft's security advisory for affected versionsCheck Version:
Get-SPFarm | Select BuildVersion (PowerShell) or check SharePoint Central Administration > System Settings > Manage servers in this farmVerify Fix Applied:
Verify security update is installed through Windows Update history or SharePoint Central Administration > Upgrade and Migration > Check product and patch installation status📡 Detection & Monitoring
Log Indicators:
- Unusual authenticated user activity patterns
- Multiple failed authentication attempts followed by successful login
- Unexpected process execution on SharePoint servers
Network Indicators:
- Unusual outbound data transfers from SharePoint servers
- Anomalous authenticated user behavior patterns
SIEM Query:
source="SharePoint" AND (event_type="ProcessCreation" OR event_type="FileAccess") AND user!="SYSTEM" AND user!="NETWORK SERVICE"