CVE-2026-20958
📋 TL;DR
This Server-Side Request Forgery (SSRF) vulnerability in Microsoft Office SharePoint allows authenticated attackers to make the server send requests to internal systems, potentially exposing sensitive information. Organizations using affected SharePoint versions are at risk, particularly those with internal network resources accessible from the SharePoint server.
💻 Affected Systems
- Microsoft Office SharePoint Server
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Attacker accesses internal services, steals credentials, or pivots to compromise other internal systems via SharePoint server.
Likely Case
Information disclosure from internal APIs, metadata services, or cloud instance metadata accessible to the SharePoint server.
If Mitigated
Limited impact due to network segmentation, egress filtering, and proper authentication controls on internal services.
🎯 Exploit Status
Exploitation requires authenticated access to SharePoint; complexity depends on specific SSRF vector and internal network configuration.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Not yet released
Vendor Advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-20958
Restart Required: Yes
Instructions:
1. Monitor Microsoft's security update page for patch release. 2. Apply security update through Windows Update or Microsoft Update Catalog when available. 3. Restart SharePoint services as required.
🔧 Temporary Workarounds
Network egress filtering
allRestrict outbound HTTP/HTTPS requests from SharePoint servers to only necessary external endpoints
URL validation hardening
allImplement additional validation for URL parameters in SharePoint custom applications
🧯 If You Can't Patch
- Implement strict network segmentation to isolate SharePoint servers from sensitive internal systems
- Deploy web application firewall (WAF) rules to detect and block SSRF patterns in SharePoint requests
🔍 How to Verify
Check if Vulnerable:
Check SharePoint version against Microsoft's security bulletin when releasedCheck Version:
Get-SPFarm | Select BuildVersionVerify Fix Applied:
Verify SharePoint version matches patched version in Microsoft advisory📡 Detection & Monitoring
Log Indicators:
- Unusual outbound HTTP requests from SharePoint server to internal IP ranges
- Multiple failed authentication attempts to internal services from SharePoint server
Network Indicators:
- HTTP requests from SharePoint server to internal metadata services (169.254.169.254, etc.)
- Unexpected connections from SharePoint to database or management ports
SIEM Query:
source="sharepoint" AND (dest_ip=10.0.0.0/8 OR dest_ip=172.16.0.0/12 OR dest_ip=192.168.0.0/16 OR dest_ip=169.254.169.254) AND http_request