CVE-2026-64916 in SharePoint Server
Summary
by MITRE • 08/11/2026
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 • 08/11/2026
Cross-site scripting vulnerabilities represent one of the most prevalent and dangerous web application security flaws, fundamentally compromising the integrity of user sessions and data confidentiality. This particular vulnerability exists within Microsoft Office SharePoint platforms where input validation mechanisms fail to properly sanitize user-supplied data during web page generation processes. The flaw enables attackers to inject malicious scripts that execute within the context of other users' browsers, creating a persistent threat vector that can be exploited across multiple sessions.
The technical implementation of this vulnerability stems from insufficient input filtering and output encoding practices within SharePoint's content rendering subsystem. When legitimate users submit data through various interface elements such as forms, comments, or web part configurations, the system fails to adequately neutralize potentially malicious content before incorporating it into dynamically generated HTML pages. This weakness creates an environment where attacker-controlled scripts can be seamlessly integrated into otherwise trusted web pages, effectively bypassing standard browser security measures designed to prevent cross-domain script execution.
From an operational perspective, this vulnerability enables sophisticated attack scenarios including session hijacking, credential theft, and unauthorized administrative actions within the SharePoint environment. Attackers can craft malicious payloads that appear legitimate to end users while simultaneously executing malicious code that exfiltrates sensitive information or performs unauthorized operations on behalf of victims. The impact extends beyond simple data theft to encompass complete compromise of user sessions and potential lateral movement within network environments where SharePoint serves as a central collaboration platform.
The vulnerability aligns with CWE-79, which specifically addresses Cross-Site Scripting flaws in web applications, and maps directly to ATT&CK technique T1566.001 for initial access through spearphishing attachments or links. Organizations utilizing SharePoint platforms face heightened risk due to the widespread use of these systems for internal collaboration, document management, and business process automation. The exploitation potential increases significantly when considering that SharePoint often serves as a gateway to enterprise resources and privileged information systems.
Mitigation strategies should encompass comprehensive input validation frameworks that employ strict encoding mechanisms for all user-supplied content before rendering in web contexts. Implementation of Content Security Policy headers, proper output encoding, and regular security assessments form essential defensive measures against such vulnerabilities. Organizations must also implement robust monitoring capabilities to detect anomalous script execution patterns and maintain up-to-date security patches from Microsoft to address known exploitation vectors. Regular employee training on recognizing social engineering attempts and implementing multi-factor authentication further reduces the overall attack surface and potential impact of successful XSS exploitation attempts.