CVE-2026-55019 in SharePoint
Summary
by MITRE • 07/14/2026
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 • 07/15/2026
Cross-site scripting vulnerabilities represent one of the most prevalent and dangerous classes of web application security flaws, with the specific weakness described affecting Microsoft Office SharePoint systems. This vulnerability falls under the CWE-79 category known as "Improper Neutralization of Input During Web Page Generation ('Cross-Site Scripting')", which occurs when web applications fail to properly sanitize user-supplied data before incorporating it into dynamically generated web pages. The flaw specifically manifests during the web page generation process where SharePoint fails to adequately neutralize malicious input, allowing attackers to inject harmful scripts that execute in the context of other users' browsers.
The security implications of this vulnerability extend beyond simple data theft or defacement, as it enables sophisticated attack vectors including session hijacking, credential theft, and unauthorized access to sensitive corporate information. An attacker with authorized access can leverage this weakness to perform network-based spoofing operations, creating a false sense of trust among legitimate users while simultaneously compromising their security posture. The attack typically involves crafting malicious input that gets processed by SharePoint's web generation engine, where the system fails to properly escape or encode special characters that could be interpreted as executable code by web browsers.
The operational impact of this vulnerability is particularly severe in enterprise environments where SharePoint serves as a central collaboration and document management platform. Attackers can exploit this weakness to inject malicious scripts that persist across multiple user sessions, potentially compromising thousands of users within an organization. The attack surface expands when considering that SharePoint often hosts sensitive business data, employee information, and confidential communications, making successful exploitation particularly damaging from both a security and business continuity perspective.
Organizations should implement comprehensive mitigations including input validation and output encoding mechanisms to prevent malicious content from being rendered as executable code. Security controls should focus on implementing strict sanitization of all user inputs before processing, employing Content Security Policy headers, and utilizing web application firewalls specifically configured to detect and block XSS attacks. The mitigation strategy should also incorporate regular security assessments and penetration testing to identify potential exploitation vectors within SharePoint environments. Additionally, Microsoft recommends applying the latest security patches and updates as they become available, while implementing proper access controls and privilege management to limit potential damage from successful exploitation attempts. This vulnerability demonstrates the critical importance of maintaining robust input validation mechanisms in web applications, as even authorized users with legitimate access can leverage such weaknesses to compromise entire systems through sophisticated social engineering and technical exploitation techniques.