CVE-2021-34467 in SharePoint Server
Summary
by MITRE • 07/17/2021
Microsoft SharePoint Server Remote Code Execution Vulnerability This CVE ID is unique from CVE-2021-34468, CVE-2021-34520.
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Analysis
by VulDB Data Team • 07/11/2026
Microsoft SharePoint Server contains a remote code execution vulnerability that arises from improper validation of user-supplied input within the web application framework. This flaw exists in the way SharePoint processes certain HTTP requests and handles file uploads, creating an opportunity for attackers to execute arbitrary code on affected systems with the privileges of the SharePoint service account. The vulnerability stems from insufficient sanitization of file names and content types during the upload process, allowing malicious payloads to be delivered and executed within the server environment.
The technical implementation of this vulnerability involves a combination of input validation bypass techniques and path traversal mechanisms that enable attackers to place malicious files in directories accessible by the SharePoint application pool. When these files are subsequently processed or accessed through the web interface, they trigger code execution without proper authorization checks. This type of flaw aligns with CWE-20, which addresses improper input validation, and represents a critical weakness in the application's security controls that directly enables remote code execution capabilities.
Operational impact of this vulnerability extends beyond simple privilege escalation as it provides attackers with persistent access to enterprise environments where SharePoint servers typically operate with elevated privileges. The compromised systems may serve as launch points for lateral movement within networks, allowing threat actors to access additional resources such as databases, file shares, and other server infrastructure. Attackers can leverage this vulnerability to establish backdoors, exfiltrate sensitive data, or deploy additional malicious tools throughout the enterprise network.
Security mitigations for this vulnerability require immediate implementation of Microsoft security patches and updates released through the regular security bulletin process. Organizations should also implement network segmentation controls that limit direct access to SharePoint servers from untrusted networks, deploy web application firewalls with content filtering capabilities, and establish robust monitoring for suspicious file upload activities. Additionally, implementing principle of least privilege configurations for SharePoint service accounts and conducting regular security assessments using tools such as those aligned with the ATT&CK framework will help detect and prevent exploitation attempts. The vulnerability demonstrates the critical importance of maintaining up-to-date security controls and proper input validation mechanisms in enterprise web applications to prevent successful exploitation of remote code execution flaws.