CVE-2018-8155 in SharePoint Enterprise Server
Summary
by MITRE
An elevation of privilege vulnerability exists when Microsoft SharePoint Server does not properly sanitize a specially crafted web request to an affected SharePoint server, aka "Microsoft SharePoint Elevation of Privilege Vulnerability." This affects Microsoft SharePoint. This CVE ID is unique from CVE-2018-8149, CVE-2018-8156, CVE-2018-8168.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 03/11/2023
The vulnerability described in CVE-2018-8155 represents a critical elevation of privilege flaw within Microsoft SharePoint Server that arises from inadequate input validation mechanisms. This security weakness specifically manifests when the affected SharePoint server fails to properly sanitize web requests containing maliciously crafted content, allowing unauthorized users to escalate their privileges and gain elevated access rights within the system. The vulnerability exists at the application layer where user-supplied data is processed without sufficient validation, creating a pathway for attackers to exploit the system's trust model and execute unauthorized operations with higher privileges than initially granted.
The technical implementation of this vulnerability stems from insufficient sanitization of web requests within the SharePoint Server's request processing pipeline. When a malicious user submits a specially crafted web request containing crafted parameters or malformed input, the server's validation mechanisms fail to properly filter or escape the input before processing. This allows attackers to inject malicious content that can manipulate the server's behavior and potentially execute arbitrary code or access restricted resources. The flaw is particularly dangerous because it operates at the point where user requests are interpreted and processed, making it difficult to detect and prevent without proper input validation controls. This type of vulnerability is classified under CWE-20 as "Improper Input Validation" and aligns with ATT&CK technique T1068 which describes "Exploitation for Privilege Escalation" through the manipulation of application-level inputs.
The operational impact of CVE-2018-8155 is significant as it enables attackers to move beyond standard user privileges to achieve administrative access within the SharePoint environment. Once exploited, an attacker could gain the ability to modify or delete content, access confidential documents, create new user accounts, or even escalate to system-level privileges depending on the underlying infrastructure configuration. This vulnerability particularly affects organizations that rely heavily on SharePoint for document management and collaboration, as it could lead to complete compromise of the SharePoint farm and potentially broader network access if the server has elevated privileges. The attack vector typically involves sending malicious HTTP requests to SharePoint endpoints, which could be executed through various means including phishing attacks, compromised web applications, or direct exploitation of exposed SharePoint services.
Organizations should implement multiple layers of defense to mitigate this vulnerability, beginning with immediate application of Microsoft's security patches and updates. The recommended mitigation strategy includes configuring proper input validation at all entry points within SharePoint applications, implementing web application firewalls to filter malicious requests, and conducting regular security assessments of SharePoint configurations. Additionally, organizations should enforce least privilege principles and ensure that SharePoint servers operate with minimal required permissions to reduce the potential impact of exploitation. Network segmentation and monitoring solutions should be deployed to detect anomalous requests that may indicate exploitation attempts. The vulnerability's exploitation risk is heightened in environments where SharePoint servers are directly exposed to external networks, making proper network security controls essential for preventing unauthorized access and privilege escalation attempts that leverage this specific flaw.