CVE-2023-29357
📋 TL;DR
CVE-2023-29357 is a critical elevation of privilege vulnerability in Microsoft SharePoint Server that allows attackers to bypass authentication and gain administrative access. This affects organizations running vulnerable SharePoint Server versions, potentially exposing sensitive data and systems. The vulnerability is particularly dangerous because it can be exploited without authentication.
💻 Affected Systems
- Microsoft SharePoint Server
- Microsoft SharePoint Foundation
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of SharePoint Server with administrative privileges, enabling data theft, ransomware deployment, lateral movement to other systems, and persistent backdoor installation.
Likely Case
Unauthenticated attackers gaining administrative access to SharePoint sites, accessing sensitive documents, user credentials, and potentially pivoting to other enterprise systems.
If Mitigated
Limited impact with proper network segmentation, strong authentication requirements, and monitoring in place, though risk remains significant until patched.
🎯 Exploit Status
Exploitation is straightforward and has been observed in the wild. Attackers can chain this with other vulnerabilities for greater impact.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: May 2023 security updates or later
Vendor Advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2023-29357
Restart Required: Yes
Instructions:
1. Apply the May 2023 security updates for SharePoint Server from Microsoft Update. 2. Restart the SharePoint servers. 3. Test functionality after patching. 4. Consider applying additional security updates if behind on patching.
🔧 Temporary Workarounds
Disable Anonymous Authentication
windowsConfigure SharePoint to require authentication for all access, reducing attack surface
Configure in SharePoint Central Administration > Security > Configure anonymous access
Network Segmentation
allRestrict access to SharePoint servers using firewalls and network controls
🧯 If You Can't Patch
- Isolate SharePoint servers from internet access and restrict internal network access
- Implement strict monitoring and alerting for suspicious authentication attempts and privilege escalation activities
🔍 How to Verify
Check if Vulnerable:
Check SharePoint version and patch level. If running SharePoint Server 2013 SP1, 2016, or 2019 without May 2023 security updates, you are vulnerable.Check Version:
Get-SPFarm | Select BuildVersion (PowerShell) or check Central Administration > Upgrade and Migration > Check product and patch installation statusVerify Fix Applied:
Verify that May 2023 security updates are installed via Windows Update history or by checking SharePoint version/build numbers.📡 Detection & Monitoring
Log Indicators:
- Unusual authentication patterns
- Unexpected administrative privilege assignments
- Suspicious SharePoint API calls
Network Indicators:
- Unusual traffic patterns to SharePoint authentication endpoints
- Requests bypassing normal authentication flows
SIEM Query:
source="sharepoint" AND (event_id=4624 OR event_id=4625) AND (privileges_assigned="Administrator" OR target_user="*admin*")