CVE-2026-55034 in SharePoint Server
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 • 07/14/2026
Cross-site scripting vulnerabilities in Microsoft Office SharePoint represent a critical security flaw that enables authenticated attackers to manipulate web page generation processes through improperly neutralized input data. This vulnerability specifically affects the way SharePoint handles user-supplied information during page rendering, creating opportunities for malicious actors to inject harmful scripts into web content. The weakness stems from insufficient sanitization of input parameters that are subsequently processed and displayed within SharePoint-generated web pages, allowing attackers to exploit this gap in the application's security controls.
The technical implementation of this vulnerability involves the failure to properly encode or escape user-provided data before incorporating it into dynamic web content. When SharePoint processes requests containing malicious input, the system does not adequately validate or sanitize the data flow through its rendering engine, resulting in the execution of unauthorized scripts within the context of other users' browsers. This occurs because the application assumes that all input from authenticated users is trustworthy and fails to implement proper input validation mechanisms that would prevent malicious payloads from being executed. The flaw typically manifests when attackers submit specially crafted content through SharePoint forms, list items, or web part configurations where user input directly influences HTML generation.
The operational impact of this vulnerability extends beyond simple data manipulation, as it enables sophisticated attack vectors including session hijacking, credential theft, and unauthorized access to sensitive organizational information. Attackers can leverage this weakness to create malicious pages that appear legitimate to end users, facilitating social engineering campaigns that exploit the trust relationship between SharePoint and its users. The vulnerability is particularly dangerous in enterprise environments where SharePoint serves as a central collaboration platform, as successful exploitation could allow attackers to escalate privileges within the SharePoint environment or gain access to restricted content. Additionally, the spoofing capabilities enable attackers to modify web page content in real-time, potentially compromising the integrity of shared information and undermining user confidence in the system.
Security professionals should implement comprehensive mitigation strategies that address both the immediate vulnerability and underlying architectural weaknesses. The primary defense involves implementing robust input validation and output encoding mechanisms throughout the SharePoint application stack, ensuring that all user-supplied data undergoes proper sanitization before being processed or displayed. Organizations must also deploy web application firewalls to monitor and filter suspicious traffic patterns that may indicate exploitation attempts. According to CWE standards, this vulnerability maps directly to CWE-79 which specifically addresses cross-site scripting flaws in web applications. The ATT&CK framework categorizes this issue under T1566 - Phishing and T1071.004 - Application Layer Protocol: Web Protocols, highlighting the network-based attack vectors that exploit these weaknesses. Microsoft recommends applying security patches promptly, implementing proper access controls, and conducting regular security assessments to identify potential exploitation paths within SharePoint environments. Organizations should also consider deploying content security policies and monitoring for unusual data submission patterns that may indicate attempted exploitation of this vulnerability.