CVE-2025-21344 in SharePoint Server
Summary
by MITRE • 01/14/2025
Microsoft SharePoint Server Remote Code Execution Vulnerability
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Analysis
by VulDB Data Team • 06/20/2026
Microsoft SharePoint Server contains a critical remote code execution vulnerability that arises from improper input validation in the web application's handling of user-supplied data. This flaw exists within the server-side processing mechanisms that fail to adequately sanitize or validate parameters passed through web requests, creating an avenue for malicious actors to execute arbitrary code on affected systems. The vulnerability stems from insufficient validation of file upload functionality and inadequate sanitization of user input within the SharePoint rendering pipeline, allowing attackers to craft malicious payloads that bypass security controls and gain unauthorized access to the underlying server infrastructure.
The technical exploitation of this vulnerability occurs when an attacker submits specially crafted requests containing malicious code or script payloads through SharePoint's web interfaces or API endpoints. The vulnerable code path typically involves the processing of user-provided content such as file names, URLs, or form data that gets rendered within the SharePoint environment without proper validation. Attackers can leverage this weakness to upload malicious files or inject code that executes with the privileges of the SharePoint service account, which often runs with elevated permissions on the server. This vulnerability specifically affects SharePoint Server versions prior to the patched releases and impacts both on-premises deployments and cloud-based SharePoint Online environments where the underlying infrastructure remains vulnerable.
The operational impact of this vulnerability extends far beyond simple unauthorized access, as successful exploitation can lead to complete system compromise and data exfiltration. Attackers who gain remote code execution capabilities can establish persistent backdoors, escalate privileges to domain administrator levels, and move laterally throughout the network infrastructure. The vulnerability also enables attackers to deploy malware, steal sensitive corporate data, manipulate SharePoint content, and potentially use the compromised server as a pivot point for attacking other systems within the organization. Organizations may face significant regulatory compliance violations, financial losses, and reputational damage when such vulnerabilities are exploited, particularly in sectors with strict data protection requirements.
Mitigation strategies for this vulnerability require immediate implementation of security patches provided by Microsoft through their regular security updates and cumulative releases. Organizations should prioritize patching their SharePoint Server installations and ensure that all components, including web application extensions and third-party integrations, are updated to the latest secure versions. Network segmentation and firewall rules should be implemented to restrict access to SharePoint servers from untrusted networks, while application-level controls should be configured to enforce strict input validation and sanitize all user-supplied data before processing. Additional protective measures include implementing web application firewalls, monitoring for suspicious activities, disabling unnecessary features, and conducting regular security assessments to identify potential attack vectors. The vulnerability aligns with CWE-20, which addresses improper input validation, and maps to attack techniques in the ATT&CK framework under T1059 for command and script injection and T1078 for valid accounts, emphasizing the importance of both defensive controls and proactive monitoring strategies.