CVE-2021-40482 in SharePoint Server
Summary
by MITRE • 10/13/2021
Microsoft SharePoint Server Information Disclosure Vulnerability
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Analysis
by VulDB Data Team • 10/15/2021
Microsoft SharePoint Server contains an information disclosure vulnerability that arises from improper handling of certain HTTP requests within the web application framework. This flaw allows authenticated attackers with limited privileges to retrieve sensitive information that should be restricted to authorized users only. The vulnerability specifically affects SharePoint Server 2016 and SharePoint Server 2019 versions where the authentication and authorization mechanisms fail to properly validate request parameters, leading to unauthorized data exposure.
The technical root cause of this vulnerability stems from inadequate input validation and access control enforcement within SharePoint's HTTP request processing pipeline. When certain web requests are processed through the SharePoint infrastructure, the system does not sufficiently verify whether the requesting user has proper authorization to access the targeted resources. This weakness enables attackers to craft malicious requests that bypass normal security boundaries and extract information that would otherwise be protected by the system's permission model. The flaw operates at the application layer and specifically impacts how SharePoint handles specific query parameters and request headers during content retrieval operations.
The operational impact of this vulnerability extends beyond simple data exposure as it provides attackers with valuable intelligence about the internal structure of SharePoint environments. An attacker who successfully exploits this vulnerability could potentially discover user account information, document paths, system configurations, and other sensitive metadata that would aid in planning further attacks. This information disclosure could facilitate subsequent exploitation attempts such as privilege escalation or lateral movement within the network. The vulnerability is particularly concerning in enterprise environments where SharePoint servers often contain sensitive business data and administrative information.
Organizations should implement immediate mitigations including applying the relevant Microsoft security updates that address this specific vulnerability. The patch released by Microsoft resolves the authentication bypass issue by strengthening input validation and access control checks within the SharePoint request processing framework. Additionally, administrators should review and tighten SharePoint permission settings to minimize the potential impact of any successful exploitation attempts. Network segmentation and monitoring solutions should be deployed to detect anomalous access patterns that might indicate exploitation attempts. The vulnerability aligns with CWE-200, which addresses improper information disclosure, and could be categorized under ATT&CK technique T1087.001 for account discovery and T1069.001 for permission groups discovery. Regular security assessments and penetration testing should be conducted to verify that the implemented controls effectively prevent unauthorized information access.