CVE-2020-1106 in SharePoint Enterprise Server
Summary
by MITRE • 01/25/2023
A cross-site-scripting (XSS) vulnerability exists when Microsoft SharePoint Server does not properly sanitize a specially crafted web request to an affected SharePoint server, aka 'Microsoft Office SharePoint XSS Vulnerability'. This CVE ID is unique from CVE-2020-1099, CVE-2020-1100, CVE-2020-1101.
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Analysis
by VulDB Data Team • 02/28/2025
The vulnerability described in CVE-2020-1106 represents a critical cross-site scripting flaw within Microsoft SharePoint Server that enables attackers to execute malicious scripts in the context of authenticated users. This vulnerability specifically manifests when the SharePoint server fails to adequately sanitize web requests containing crafted malicious input, creating an avenue for persistent security breaches. The flaw affects Microsoft Office SharePoint Server implementations and operates at the application layer where user input is processed without proper validation mechanisms. Security researchers have identified this as a significant threat vector that could compromise user sessions and potentially lead to broader system infiltration. The vulnerability is particularly concerning because it affects the core functionality of SharePoint's web request handling mechanisms, where user-supplied data should be rigorously filtered before processing.
The technical exploitation of this XSS vulnerability occurs when an attacker crafts a malicious web request that contains script payloads designed to bypass SharePoint's input sanitization controls. This typically involves injecting malicious javascript code or other script elements into parameters that are then rendered back to users without proper encoding or validation. The vulnerability stems from insufficient input validation and output encoding practices within SharePoint's server-side processing logic, allowing malicious content to persist in the application's response. According to CWE classification, this represents a CWE-79: "Cross-site Scripting" vulnerability, which is categorized under the broader category of input validation and output encoding flaws. The flaw operates at the intersection of web application security and user session management, where the absence of proper sanitization creates persistent attack surfaces.
The operational impact of this vulnerability extends beyond simple script execution to encompass potential session hijacking, data theft, and privilege escalation within the SharePoint environment. An attacker who successfully exploits this vulnerability can manipulate user sessions, gain unauthorized access to sensitive information, and potentially execute administrative commands within the SharePoint server. The attack surface is particularly wide given that SharePoint servers typically host critical business data and user authentication mechanisms. This vulnerability aligns with ATT&CK technique T1190: "Exploit Public-Facing Application" as it targets publicly accessible SharePoint services. Organizations may experience unauthorized access to documents, user credentials, and internal network resources, with potential for lateral movement once initial access is achieved through this XSS vector.
Mitigation strategies for CVE-2020-1106 should prioritize immediate implementation of Microsoft security patches and updates to address the identified sanitization gaps. Organizations must implement comprehensive input validation mechanisms that enforce strict encoding of user-supplied data before processing, particularly for parameters that are rendered back to users. Web application firewalls should be configured to detect and block suspicious script payloads in incoming requests, while security headers including Content Security Policy should be enforced to prevent script execution. Regular security assessments and code reviews should focus on input validation controls, with particular attention to areas where user data is processed and displayed. Network segmentation and access controls should be implemented to limit potential damage from successful exploitation attempts, while user education regarding phishing and social engineering attacks remains crucial. The vulnerability demonstrates the importance of defense-in-depth strategies and continuous security monitoring to detect and respond to exploitation attempts against SharePoint server environments.