CVE-2026-69417 in SharePoint Server
Summary
by MITRE • 09/09/2026
Improper neutralization of input during web page generation ('cross-site scripting') in Microsoft Office SharePoint allows an authorized attacker to perform spoofing over a network.
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Analysis
by VulDB Data Team • 09/09/2026
The vulnerability described constitutes a classic instance of improper neutralization of input during web page generation, commonly known as Cross-Site Scripting or XSS. This flaw resides within the core processing logic of Microsoft Office SharePoint Server, specifically in how user-supplied data is handled before being rendered into HTML content for the client browser. The fundamental technical error involves the failure to adequately sanitize, validate, or encode special characters such as angle brackets, quotation marks, and ampersands that are part of the HTML syntax. When an authorized attacker injects malicious script code through input fields, query parameters, or other data entry points within the SharePoint interface, the server processes this input without applying necessary security filters. Consequently, when the web page is generated and sent to a victim user's browser, the embedded scripts execute in the context of the trusted domain associated with the SharePoint installation. This execution environment grants the malicious script full access to the Document Object Model (DOM) and session cookies of the authenticated user, effectively bypassing same-origin policy restrictions that are designed to isolate web applications from one another.
The operational impact of this vulnerability is significant because it allows an attacker who has valid credentials within the SharePoint environment to perform spoofing attacks over a network. Spoofing in this context typically refers to session hijacking or identity impersonation, where the attacker can steal sensitive authentication tokens and cookies stored by the browser. By capturing these credentials, the attacker can masquerade as legitimate users, gaining unauthorized access to confidential documents, lists, and site configurations that would otherwise be protected by SharePoint's permission model. Furthermore, because the attack is executed via client-side scripting, it does not require direct exploitation of server-side vulnerabilities or network-level intrusions beyond standard web traffic interception if session tokens are transmitted insecurely. The attacker can also manipulate page content dynamically to phish for additional credentials from other users who view the compromised pages, creating a chain reaction of compromise within the organization's internal network infrastructure.
From an industry standards perspective, this vulnerability maps directly to CWE-79: Improper Neutralization of Input During Web Page Generation (Cross-site Scripting). This classification highlights the failure in input validation and output encoding processes that are critical for web application security. In terms of offensive tactics, the exploitation aligns with MITRE ATT&CK techniques related to Client-side Rendering and potentially Account Manipulation if used to persist access or steal credentials. The attack vector is classified as Network-based but requires local user interaction or prior authentication within the SharePoint environment, placing it in a medium-risk category regarding initial access but high risk for lateral movement once inside the perimeter.
Mitigation strategies must address both immediate remediation and long-term architectural improvements. Immediately, Microsoft should apply available security patches that update the input validation libraries used by SharePoint to ensure all user inputs are properly encoded before being rendered as HTML output. This includes implementing strict Content Security Policy (CSP) headers which can restrict the sources from which scripts are allowed to execute, thereby neutralizing many XSS attacks even if they slip through initial filters. Administrators should also enforce least-privilege access controls, ensuring that users with write permissions do not have excessive rights that could be leveraged for broader spoofing or data exfiltration activities. Long-term defenses involve adopting secure coding practices such as output encoding based on context (HTML, JavaScript, CSS, URL) and utilizing modern frameworks that automatically handle escaping of dynamic content. Regular security audits and penetration testing focused on input validation flaws are essential to identify similar vulnerabilities before they can be exploited in production environments.