CVE-2026-70267 in SharePoint Server
Summary
by MITRE • 10/14/2026
Inclusion of functionality from untrusted control sphere in Microsoft Office SharePoint allows an authorized attacker to execute code over a network.
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Analysis
by VulDB Data Team • 10/14/2026
The vulnerability described involves a critical flaw within the architecture of Microsoft Office SharePoint, specifically related to how the application handles external inputs and integrates third-party or user-supplied components. This issue stems from a failure to properly validate the source and integrity of functionality before inclusion in the execution context. In secure software design principles, applications must strictly enforce boundaries between trusted internal code and untrusted external data. When an application includes functionality from an uncontrolled sphere without rigorous verification, it creates a pathway for malicious actors to inject harmful logic into the system's runtime environment. This specific flaw allows an attacker who has valid authentication credentials to exploit this lack of isolation, effectively bypassing standard security controls that rely on user privilege levels rather than input validation integrity.
From a technical perspective, this vulnerability aligns with CWE-94, which describes Improper Control of Generation of Code or Command, often referred to as code injection. The core mechanism involves the application accepting data from an untrusted source and using it to construct executable commands or include external scripts without adequate sanitization. In the context of SharePoint, this might manifest through custom web parts, uploaded files with embedded malicious macros, or manipulated configuration settings that reference external resources. Because the vulnerability requires authentication, it is classified as a remote code execution flaw accessible only by authorized users. However, since many enterprise environments grant broad access to internal portals for various departments and contractors, the pool of potential attackers is significantly larger than in unauthenticated scenarios. The attacker leverages this authenticated access to trigger the inclusion of malicious functionality, which then executes with the privileges of the SharePoint service account or the user context, depending on how the application processes the injected code.
The operational impact of such a vulnerability is severe and multifaceted. Once an attacker achieves remote code execution within the SharePoint environment, they gain the ability to manipulate data, exfiltrate sensitive corporate information, install additional malware, or use the server as a pivot point for further network intrusion. This compromises the confidentiality, integrity, and availability of the organization's content management systems. Furthermore, because SharePoint often integrates with other enterprise services such as Active Directory and SQL Server, compromising one instance can lead to lateral movement across the entire IT infrastructure. The presence of this flaw undermines trust in the platform’s ability to isolate user-generated content from system-level operations, potentially leading to significant financial loss, regulatory penalties under standards like GDPR or HIPAA if personal data is exposed, and reputational damage due to perceived security negligence.
To mitigate this risk, organizations must implement a defense-in-depth strategy focusing on input validation and least privilege principles. Developers should ensure that all external inputs are strictly validated against expected formats using allow-listing techniques rather than block-listing. Functionality from untrusted sources should never be dynamically included or executed without explicit administrative approval and sandboxing mechanisms. For existing deployments, applying the latest security patches provided by Microsoft is essential to address known implementation flaws in SharePoint’s handling of external resources. Additionally, network segmentation can limit the blast radius if an exploit occurs, ensuring that compromised servers cannot easily communicate with critical backend databases or domain controllers. Regular vulnerability assessments and penetration testing focused on authenticated web application attacks will help identify similar misconfigurations before they are exploited by malicious actors. Monitoring logs for unusual activity related to file uploads or script executions can also provide early detection of exploitation attempts aligned with ATT&CK techniques such as T1059 Command and Scripting Interpreter or T1190 Exploit Public-Facing Application, although the latter typically refers to unauthenticated access, making this specific case more relevant to insider threats or compromised credentials.