CVE-2026-88206 in SharePoint Server
Summary
by MITRE • 10/14/2026
Server-side request forgery (ssrf) in Microsoft Office SharePoint allows an authorized attacker to elevate privileges over a network.
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Analysis
by VulDB Data Team • 10/14/2026
The vulnerability described constitutes a Server-Side Request Forgery flaw within the Microsoft Office SharePoint infrastructure, representing a significant security risk that enables privilege escalation through network-based exploitation techniques. This type of attack exploits the server's trust in user-supplied input by allowing an attacker to instruct the backend system to make HTTP requests to arbitrary destinations. In the context of SharePoint, this typically involves manipulating parameters or headers within web requests processed by the application server, causing it to fetch content from internal network resources that would otherwise be inaccessible to external users. The core technical flaw lies in the insufficient validation and sanitization of input data before it is used to construct outbound network connections. When an authorized user provides a URL or endpoint reference, the system fails to adequately verify whether the target address resides within an allowed whitelist or belongs to a restricted internal zone. This lack of strict access control over server-side requests allows the attacker to bypass perimeter defenses and interact with backend services, databases, or administrative interfaces that are not directly exposed to the public internet.
The operational impact of this vulnerability is severe due to its potential for privilege escalation. Although the initial entry point requires authentication as an authorized user, the ability to forge requests from the server itself effectively grants the attacker a foothold within the internal network segment where SharePoint resides. By directing the server to communicate with sensitive internal endpoints, such as metadata services, configuration management systems, or other microservices running on localhost or private IP ranges, the attacker can extract confidential data, manipulate system configurations, or execute further attacks against more privileged components of the infrastructure. This capability undermines the principle of least privilege and allows a standard user account to act with elevated permissions by leveraging the server's own identity and network access rights. The attack vector aligns closely with CWE-918, which defines Server-Side Request Forgery as a weakness where an application retrieves data from a remote resource without validating the destination URL, leading to unauthorized information disclosure or system compromise.
From a tactical perspective, this vulnerability maps directly to several techniques within the MITRE ATT&CK framework, particularly those related to Discovery and Lateral Movement. The initial phase of identifying internal services corresponds to T1046 Network Service Scanning, where the attacker uses the server as a proxy to map out the internal network topology. Subsequent interactions with specific backend APIs or administrative interfaces may fall under T1583 Acquire Infrastructure or T1210 Exploitation of Remote Services, depending on how the forged requests are utilized to exploit other weaknesses in connected systems. The ability to escalate privileges through this mechanism highlights a critical gap in identity and access management controls within the SharePoint deployment architecture. It demonstrates that even authenticated users can leverage server-side logic flaws to transcend their assigned role boundaries, effectively turning a low-privilege account into a high-impact threat actor capable of influencing core system operations.
Mitigation strategies must focus on implementing robust input validation and strict network segmentation policies. Administrators should enforce allow-listing for all outbound URLs initiated by the SharePoint server, ensuring that only known and trusted internal endpoints are accessible via SSRF-prone features such as web parts, data connections, or external content types. Additionally, deploying a reverse proxy with deep packet inspection can help filter malicious requests before they reach the application layer. Network-level controls, including firewall rules that restrict outbound traffic from SharePoint servers to specific ports and IP ranges, provide an essential defense-in-depth measure. Regular security assessments and code reviews targeting SSRF vulnerabilities are also critical to identifying and remediating such flaws in custom solutions or third-party integrations connected to the SharePoint environment.