CVE-2020-17061 in SharePoint Server
Summary
by MITRE • 11/11/2020
Microsoft SharePoint Remote Code Execution Vulnerability
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Analysis
by VulDB Data Team • 12/05/2020
Microsoft SharePoint Server contains a remote code execution vulnerability that arises from improper validation of user input within the server-side rendering functionality. This flaw exists in the way SharePoint processes certain HTTP requests containing crafted payloads that bypass validation mechanisms. The vulnerability specifically affects the server-side include functionality where untrusted input is directly processed without adequate sanitization, allowing attackers to inject malicious code that executes within the context of the SharePoint application pool. The issue stems from a lack of proper input filtering and validation routines that should have been implemented to prevent arbitrary code execution. According to CWE-20, this represents a classic input validation vulnerability where insufficient checks allow malicious data to be processed as executable code. The attack surface is particularly wide given that SharePoint Server is commonly deployed in enterprise environments where it handles sensitive data and user authentication. This vulnerability enables attackers to execute arbitrary commands on the affected server, potentially leading to full system compromise and lateral movement within the network. The exploitation requires a maliciously crafted HTTP request that leverages the server-side rendering engine to execute malicious code. This type of vulnerability aligns with ATT&CK technique T1059.001 for command and script injection, as well as T1078.004 for valid accounts, since successful exploitation often requires legitimate credentials to access the SharePoint services. The vulnerability impacts multiple SharePoint Server versions including 2016, 2019, and SharePoint Online, making it particularly concerning for organizations with extensive SharePoint deployments. The root cause lies in the insufficient sanitization of input parameters within the SharePoint rendering pipeline, where user-supplied data is not properly escaped or validated before being processed by the server. Attackers can exploit this by crafting specific HTTP requests that contain malicious payloads designed to bypass the existing security controls. The vulnerability is particularly dangerous because it allows for arbitrary code execution without requiring elevated privileges, making it a high-severity issue that can lead to complete system compromise. Organizations using SharePoint Server should immediately implement the security patches provided by Microsoft to remediate this vulnerability. The patch addresses the input validation issue by implementing proper sanitization routines and strengthening the validation of user-supplied data within the server-side rendering components. Security teams should also monitor for suspicious network traffic patterns that might indicate exploitation attempts, particularly unusual HTTP requests containing encoded payloads. Additionally, implementing network segmentation and access controls can help limit the potential impact of successful exploitation attempts. The vulnerability demonstrates the critical importance of proper input validation and sanitization in web applications, as highlighted by industry best practices and security frameworks that emphasize the need for defense-in-depth strategies to prevent such critical flaws from being exploited in production environments.