CVE-2017-8514 in SharePoint Enterprise Server
Summary
by MITRE
An information disclosure vulnerability exists when Microsoft SharePoint software fails to properly sanitize a specially crafted requests, aka "Microsoft SharePoint Reflective XSS Vulnerability".
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Analysis
by VulDB Data Team • 09/13/2024
The vulnerability identified as CVE-2017-8514 represents a critical information disclosure flaw within Microsoft SharePoint software that stems from inadequate request sanitization mechanisms. This vulnerability specifically manifests as a reflective cross-site scripting issue that allows attackers to exploit the software's failure to properly validate and sanitize user input parameters. The flaw exists in the way SharePoint processes incoming HTTP requests, particularly when handling certain query string parameters or form data that are not adequately filtered or escaped before being rendered back to users. This reflective nature means that malicious input is immediately reflected back to the user without proper encoding or validation, creating an exploitable condition that can be leveraged by threat actors to inject malicious scripts into the SharePoint environment.
From a technical perspective, this vulnerability operates through the exploitation of improper input validation within SharePoint's web application layer where user-supplied data flows directly into the output generation process. The flaw typically occurs when SharePoint receives a crafted request containing malicious script code within parameters such as URL query strings, form fields, or header values. When the application processes these inputs without proper sanitization, the malicious code becomes embedded in the response sent back to the user's browser. This creates a reflective XSS condition where the malicious script executes in the context of the victim's browser session, potentially allowing attackers to steal session cookies, credentials, or perform other malicious actions on behalf of authenticated users. The vulnerability falls under CWE-79 which specifically addresses Cross-Site Scripting flaws, and aligns with ATT&CK technique T1566.001 for initial access through spearphishing attachments or links.
The operational impact of CVE-2017-8514 extends beyond simple information disclosure, as it can enable more sophisticated attacks within SharePoint environments. Attackers can leverage this vulnerability to establish persistent access by stealing session tokens or cookies that grant them elevated privileges within the SharePoint application. The reflected nature of the vulnerability means that exploitation requires user interaction, typically through phishing emails or malicious links delivered to targeted individuals. Once successfully exploited, threat actors can access sensitive documents, modify content, escalate privileges, or use the compromised SharePoint instance as a pivot point to attack other systems within the network. The vulnerability affects various versions of Microsoft SharePoint Server and can potentially impact organizations with extensive SharePoint deployments, particularly those that do not maintain up-to-date security patches.
Organizations should implement multiple layers of mitigation to address this vulnerability effectively. The primary recommendation involves applying the official Microsoft security patches released for this vulnerability, which typically include enhanced input validation and output encoding mechanisms within SharePoint's request processing pipeline. Network segmentation and web application firewalls can provide additional protection by monitoring and filtering suspicious traffic patterns that may indicate exploitation attempts. Implementing Content Security Policy headers can help prevent script execution in response to malicious inputs, while regular security monitoring should focus on detecting anomalous requests or unusual user behavior patterns that may indicate successful exploitation attempts. Administrative users should also consider implementing strict input validation policies and regularly auditing SharePoint configurations to ensure that security hardening measures are properly applied. The vulnerability demonstrates the critical importance of maintaining up-to-date security patches and implementing robust input validation mechanisms as recommended by industry standards such as the OWASP Top Ten and NIST cybersecurity frameworks.