CVE-2024-38227: Microsoft SharePoint Server RCE Vulnerability

CVE-2024-38227 Overview

CVE-2024-38227 is a remote code execution vulnerability affecting Microsoft SharePoint Server. This flaw allows an authenticated attacker with Site Owner permissions to execute arbitrary code on the vulnerable SharePoint Server instance. The vulnerability is classified as a Command Injection weakness (CWE-77), enabling attackers to inject malicious commands that the server will execute in its operational context.

Critical Impact

Successful exploitation allows remote code execution on Microsoft SharePoint Server, potentially compromising the entire SharePoint environment, sensitive corporate data, and connected systems.

Affected Products

• Microsoft SharePoint Server Subscription Edition
• Microsoft SharePoint Server 2019
• Microsoft SharePoint Server 2016 Enterprise

Discovery Timeline

• September 10, 2024 - CVE-2024-38227 published to NVD
• September 17, 2024 - Last updated in NVD database

Technical Details for CVE-2024-38227

Vulnerability Analysis

This vulnerability resides within Microsoft SharePoint Server's handling of specific server-side operations. The flaw enables command injection, where an attacker who has already obtained Site Owner privileges can craft malicious input that gets processed by the server without adequate sanitization. When this input is executed, it allows the attacker to run arbitrary commands with the privileges of the SharePoint Server process.

The attack is network-accessible and does not require user interaction, though it does require high-privilege authentication (Site Owner role). Once successfully exploited, the attacker gains the ability to impact the confidentiality, integrity, and availability of the target system, potentially leading to full system compromise.

Root Cause

The vulnerability stems from improper neutralization of special elements used in command execution (CWE-77 - Command Injection). SharePoint Server fails to adequately validate or sanitize user-controlled input before incorporating it into commands that are executed on the underlying operating system. This allows attackers with sufficient privileges to inject and execute arbitrary commands.

Attack Vector

The attack requires network access to the SharePoint Server and authentication with Site Owner permissions. An attacker would:

1. Authenticate to the SharePoint Server with an account possessing Site Owner privileges
2. Identify the vulnerable functionality that processes user input
3. Craft a malicious payload containing injected commands
4. Submit the payload through the vulnerable interface
5. The server executes the injected commands with SharePoint Server privileges

The vulnerability mechanism involves insufficient input validation in SharePoint Server's command processing logic. When Site Owner-level operations are performed, certain parameters are passed to system commands without proper sanitization, allowing command delimiter characters and additional commands to be injected. For detailed technical information, refer to the Microsoft Security Advisory.

Detection Methods for CVE-2024-38227

Indicators of Compromise

• Unusual process spawning from SharePoint Server processes (e.g., cmd.exe, powershell.exe, or other system shells)
• Unexpected outbound network connections from SharePoint Server
• Anomalous file system modifications or new files created in SharePoint directories
• Suspicious activity in SharePoint ULS logs indicating command injection attempts

Detection Strategies

• Monitor Windows Event Logs for process creation events originating from SharePoint application pools
• Implement web application firewall (WAF) rules to detect command injection patterns in HTTP requests
• Deploy endpoint detection and response (EDR) solutions to identify post-exploitation behaviors
• Review SharePoint audit logs for unusual Site Owner activities or configuration changes

Monitoring Recommendations

• Enable verbose logging for SharePoint Server and centralize logs for SIEM analysis
• Configure alerts for process creation chains where SharePoint worker processes spawn shell interpreters
• Monitor for privilege escalation attempts following initial SharePoint authentication
• Track lateral movement indicators from SharePoint Server to other network resources

How to Mitigate CVE-2024-38227

Immediate Actions Required

• Apply the Microsoft security update released in September 2024 immediately
• Review Site Owner accounts and ensure principle of least privilege is enforced
• Audit recent Site Owner activities for any suspicious behavior
• Consider temporarily restricting Site Owner permissions until patches are applied

Patch Information

Microsoft has released security updates to address this vulnerability as part of their September 2024 security release. Organizations should apply the appropriate patch for their SharePoint Server version:

• SharePoint Server Subscription Edition
• SharePoint Server 2019
• SharePoint Server 2016 Enterprise

Consult the Microsoft Security Update Guide for CVE-2024-38227 for specific patch downloads and installation instructions.

Workarounds

• Limit Site Owner permissions to only trusted administrators
• Implement network segmentation to restrict access to SharePoint Server management interfaces
• Deploy web application firewall rules to filter command injection patterns
• Monitor and restrict outbound network traffic from SharePoint Server

To verify patch installation status, use the following SharePoint Management Shell command:

# Verify SharePoint patch level
Get-SPFarm | Select BuildVersion
# Cross-reference with Microsoft's security bulletin for patched versions
# Ensure Build Version matches or exceeds the patched version for your edition