CVE-2026-64900
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 in Microsoft Office SharePoint represent a critical security weakness that enables authenticated attackers to execute malicious scripts within the context of legitimate user sessions. This vulnerability falls under the CWE-79 category, which specifically addresses cross-site scripting flaws in web applications where input validation and output encoding mechanisms fail to properly sanitize user-provided data before rendering it in web pages. The flaw occurs during the web page generation process when SharePoint fails to adequately neutralize potentially malicious input that originates from authorized users who have legitimate access to the system.
The technical implementation of this vulnerability stems from insufficient input sanitization within SharePoint's content management and rendering components. When authenticated users submit data through various SharePoint interfaces such as discussion boards, document libraries, or custom web parts, the platform does not sufficiently validate or encode this input before incorporating it into dynamically generated web pages. This allows an attacker with authorized access to inject malicious scripts that can execute in the context of other users' browsers, potentially leading to session hijacking, credential theft, or unauthorized data manipulation. The vulnerability specifically impacts SharePoint's ability to properly escape special characters and HTML entities during page generation processes.
The operational impact of this vulnerability extends beyond simple script execution, as it enables sophisticated attack vectors that can compromise entire SharePoint environments. Attackers can leverage this weakness to perform session fixation attacks, redirect users to malicious domains, or inject persistent scripts that maintain their effectiveness across multiple user sessions. The authenticated nature of the attack means that adversaries do not require external network access or special privileges beyond legitimate user accounts, making detection and prevention more challenging. This vulnerability particularly affects organizations relying on SharePoint for collaborative environments where users frequently contribute content through web interfaces.
Mitigation strategies should focus on implementing comprehensive input validation and output encoding mechanisms throughout the SharePoint platform. Organizations must ensure that all user-provided data undergoes strict sanitization before being rendered in web pages, with particular attention to cross-site scripting prevention measures such as HTML entity encoding, Content Security Policy implementation, and proper input validation routines. Microsoft recommends applying security patches promptly, enabling enhanced security features within SharePoint, and implementing network-level protections such as web application firewalls to monitor for suspicious script injection attempts. Additionally, organizations should conduct regular security assessments and implement user access controls that limit the scope of potential exploitation while maintaining operational functionality.
The vulnerability demonstrates how even authorized users can pose significant security risks when input validation mechanisms fail within enterprise collaboration platforms. This aligns with ATT&CK technique T1566 which covers social engineering through malicious content delivery, and specifically addresses how attackers can leverage legitimate access privileges to execute attacks that would otherwise be blocked by traditional perimeter security measures. Organizations must recognize that internal threats from authenticated users present unique challenges that require both technical controls and administrative oversight to effectively mitigate.