CVE-2021-1707 in SharePoint Server
Summary
by MITRE • 01/13/2021
Microsoft SharePoint Server Remote Code Execution Vulnerability
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Analysis
by VulDB Data Team • 10/09/2024
Microsoft SharePoint Server contains a remote code execution vulnerability that arises from improper validation of user input within the web application's handling of certain HTTP requests. This flaw exists in the way SharePoint processes specific parameters in web requests, allowing attackers to inject malicious code that executes on the target server with the privileges of the SharePoint service account. The vulnerability specifically affects SharePoint Server 2016 and SharePoint Server 2019 versions, where insufficient sanitization of input parameters enables arbitrary code execution. According to CWE-20, this represents a classic input validation vulnerability where the application fails to properly sanitize or validate user-supplied data before processing. The flaw stems from inadequate boundary checking and parameter validation mechanisms within the SharePoint web processing pipeline, creating an attack surface that can be exploited through crafted HTTP requests without requiring authentication.
The operational impact of CVE-2021-1707 extends beyond simple code execution, as successful exploitation can lead to complete system compromise and lateral movement within network environments. Attackers can leverage this vulnerability to establish persistent backdoors, exfiltrate sensitive data, and potentially escalate privileges to domain administrator levels depending on the SharePoint service account permissions. The vulnerability affects the SharePoint Server's web application framework, making it particularly dangerous in enterprise environments where SharePoint serves as a central collaboration platform. Organizations running affected SharePoint versions face significant risk of data breaches, as the vulnerability allows attackers to execute arbitrary commands on the server, potentially gaining access to confidential documents, user credentials, and internal network resources. This represents a critical security gap that aligns with ATT&CK technique T1059.001 for command and script injection, and T1078 for valid accounts, as the exploitation can occur through legitimate service accounts with elevated privileges.
Mitigation strategies for CVE-2021-1707 focus on immediate patch application and network segmentation to limit potential attack vectors. Microsoft released security updates that address the input validation issues by implementing proper sanitization of user parameters and strengthening the web request handling mechanisms within SharePoint Server. Organizations should prioritize applying the relevant security patches as soon as possible, as the vulnerability has a CVSS score of 8.1, indicating high severity. Additional defensive measures include implementing network-based restrictions such as firewall rules to limit access to SharePoint servers, disabling unnecessary web features and services, and monitoring for suspicious HTTP request patterns that might indicate exploitation attempts. The vulnerability highlights the importance of proper input validation and the need for robust security controls in web applications, particularly those handling user-supplied data. Security teams should also consider implementing application whitelisting policies and regular security assessments to identify similar vulnerabilities in other web applications within the enterprise environment, as this flaw demonstrates the critical importance of maintaining up-to-date security practices and the potential consequences of inadequate input validation in enterprise collaboration platforms.