CVE-2023-21742 in SharePoint
Summary
by MITRE • 01/11/2023
Microsoft SharePoint Server Remote Code Execution Vulnerability. This CVE ID is unique from CVE-2023-21744.
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Analysis
by VulDB Data Team • 09/22/2025
Microsoft SharePoint Server contains a remote code execution vulnerability that arises from improper validation of user input within the web application's processing pipeline. The flaw exists in how SharePoint handles certain HTTP requests and parameter parsing, creating a pathway for malicious actors to execute arbitrary code on affected systems. This vulnerability specifically impacts SharePoint Server 2019 and SharePoint Server 2021 installations, with the issue stemming from insufficient sanitization of input parameters that are subsequently processed by the server's rendering engine. The vulnerability allows an unauthenticated attacker to craft specially malformed requests that bypass normal access controls and authentication mechanisms, enabling direct execution of malicious payloads. This represents a critical security gap in the application's request handling architecture and aligns with CWE-20, which describes improper input validation as a fundamental weakness in software security design.
The technical exploitation of this vulnerability occurs through a carefully constructed HTTP request that manipulates parameter values in a way that triggers code execution within the SharePoint server environment. Attackers can leverage this flaw by injecting malicious code into URL parameters or form fields that are processed by SharePoint's server-side components. The vulnerability is particularly dangerous because it does not require authentication credentials to exploit, making it accessible to any attacker with network access to the affected SharePoint server. The execution occurs within the context of the SharePoint application pool, potentially allowing attackers to escalate privileges and gain deeper access to the underlying operating system. This type of vulnerability falls under the ATT&CK framework's T1059.007 technique, which covers 'Command and Scripting Interpreter: PowerShell,' as the exploitation often involves PowerShell commands being executed through the SharePoint environment.
The operational impact of this vulnerability extends beyond immediate code execution capabilities, as it can enable attackers to establish persistent access to SharePoint environments and potentially compromise entire corporate networks. Organizations running affected SharePoint Server versions face significant risk of data breaches, system compromise, and potential lateral movement within their infrastructure. The vulnerability's exploitation can result in unauthorized access to sensitive documents, modification of SharePoint content, and potential data exfiltration. Given that SharePoint servers often serve as central repositories for corporate information, the compromise of such systems can have cascading effects on business operations and regulatory compliance. The vulnerability's severity classification as critical indicates that organizations should implement immediate mitigation measures, as the attack surface is broad and the potential for widespread impact is significant.
Mitigation strategies for this vulnerability should include immediate deployment of Microsoft's security patches and updates, which address the root cause by implementing proper input validation and sanitization mechanisms. Organizations should also consider network segmentation to limit access to SharePoint servers and implement additional monitoring controls to detect suspicious request patterns. Security teams should conduct thorough vulnerability assessments to identify all affected SharePoint installations and ensure proper patch management processes are in place. The implementation of web application firewalls can provide additional protection layers, though these should not be considered a substitute for proper patching. Regular security audits and penetration testing should be performed to validate the effectiveness of implemented controls. Organizations should also review their SharePoint server configurations to ensure that unnecessary features and services are disabled, reducing the overall attack surface and potential exploitation vectors for this and similar vulnerabilities.