CVE-2022-21837: SharePoint Foundation RCE Vulnerability

CVE-2022-21837 Overview

CVE-2022-21837 is a Remote Code Execution (RCE) vulnerability affecting Microsoft SharePoint Server. This vulnerability allows an authenticated attacker with low privileges to execute arbitrary code on the target SharePoint server through a network-based attack vector. The vulnerability requires no user interaction to exploit, making it particularly dangerous in enterprise environments where SharePoint serves as a critical collaboration and document management platform.

Critical Impact

Successful exploitation enables authenticated attackers to execute arbitrary code with the privileges of the SharePoint service account, potentially leading to complete compromise of the SharePoint environment, data exfiltration, and lateral movement within the network.

Affected Products

• Microsoft SharePoint Foundation 2013 SP1
• Microsoft SharePoint Server 2016 Enterprise
• Microsoft SharePoint Server 2019
• Microsoft SharePoint Server Subscription Edition

Discovery Timeline

• January 11, 2022 - CVE-2022-21837 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2022-21837

Vulnerability Analysis

This Remote Code Execution vulnerability in Microsoft SharePoint Server stems from improper handling of certain inputs within the SharePoint application. An attacker who has authenticated to a vulnerable SharePoint server can exploit this flaw to execute malicious code within the context of the SharePoint application pool identity.

The attack is network-accessible, meaning remote exploitation is possible once the attacker has valid credentials to the SharePoint environment. The low privilege requirement indicates that even standard user accounts with minimal SharePoint permissions may be sufficient to trigger the vulnerability. The impact is severe across all three security dimensions—confidentiality, integrity, and availability—allowing attackers to read sensitive data, modify content, and potentially disrupt SharePoint services.

Root Cause

Microsoft has classified this vulnerability under NVD-CWE-noinfo, indicating that specific weakness enumeration details have not been publicly disclosed. Based on the vulnerability class and Microsoft's SharePoint architecture, the issue likely involves improper validation or processing of user-supplied data that gets executed in a privileged context. SharePoint's complex object model and extensive API surface area have historically been vectors for similar RCE vulnerabilities.

Attack Vector

The attack leverages network access to a vulnerable SharePoint server. An authenticated user with low-level privileges can craft and submit malicious requests to the SharePoint application. Since no user interaction is required, the attack can be executed directly through API calls or crafted HTTP requests to the SharePoint web application. The exploitation does not change the scope boundary, meaning the attack affects only the SharePoint server itself, though this may be sufficient for attackers to pivot to other resources.

The vulnerability mechanism involves sending specially crafted requests to the SharePoint server that bypass input validation controls. When processed by the vulnerable component, these requests result in arbitrary code execution with the privileges of the SharePoint service account. For detailed technical information, refer to the Microsoft Security Advisory.

Detection Methods for CVE-2022-21837

Indicators of Compromise

• Unusual process execution originating from SharePoint application pool processes (w3wp.exe)
• Unexpected network connections from SharePoint servers to external or unusual internal destinations
• Anomalous PowerShell or command prompt activity spawned by IIS worker processes
• Suspicious file creation or modification in SharePoint directories outside normal operational patterns

Detection Strategies

• Monitor SharePoint ULS logs for unusual API calls or error patterns indicating exploitation attempts
• Implement network segmentation monitoring to detect lateral movement from SharePoint servers
• Deploy endpoint detection and response (EDR) solutions to identify suspicious child processes spawned by SharePoint application pools
• Review Windows Security Event logs for anomalous authentication patterns to SharePoint services

Monitoring Recommendations

• Configure alerting on unusual authentication volumes or patterns to SharePoint endpoints
• Enable detailed logging for SharePoint server-side activities and API access
• Implement file integrity monitoring on SharePoint server binaries and configuration files
• Monitor for indicators of web shell deployment or persistence mechanisms on SharePoint servers

How to Mitigate CVE-2022-21837

Immediate Actions Required

• Apply Microsoft's security updates for CVE-2022-21837 immediately across all affected SharePoint environments
• Review SharePoint user accounts and remove unnecessary privileges, following the principle of least privilege
• Audit recent SharePoint authentication logs for suspicious activity that may indicate prior exploitation
• Isolate SharePoint servers from direct internet exposure where possible, requiring VPN or other secure access methods

Patch Information

Microsoft has released security updates addressing this vulnerability as part of the January 2022 Patch Tuesday release. Administrators should consult the Microsoft Security Update Guide for CVE-2022-21837 for specific patch versions and deployment guidance for their SharePoint edition. Organizations should prioritize patching based on the network exposure and criticality of their SharePoint deployments.

Workarounds

• Restrict network access to SharePoint servers using firewall rules to limit exposure to trusted networks only
• Implement additional authentication controls such as multi-factor authentication (MFA) for SharePoint access
• Consider placing SharePoint servers behind a Web Application Firewall (WAF) to filter potentially malicious requests
• Review and tighten SharePoint permission levels to minimize the number of authenticated users with access

# Example: Verify SharePoint patch level via PowerShell
Get-SPFarm | Select BuildVersion
# Compare output against patched versions from Microsoft advisory