CVE-2021-1712 in SharePoint Server
Summary
by MITRE • 01/13/2021
Microsoft SharePoint Elevation of Privilege Vulnerability This CVE ID is unique from CVE-2021-1719.
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Analysis
by VulDB Data Team • 05/04/2025
This vulnerability affects Microsoft SharePoint Server and represents a critical elevation of privilege flaw that allows authenticated attackers to escalate their privileges within the SharePoint environment. The vulnerability stems from improper validation of user permissions and access controls within the SharePoint authentication framework, specifically impacting how the system handles user session management and privilege verification. Security researchers identified that when certain SharePoint services process user requests, they fail to adequately verify whether the requesting user possesses sufficient privileges to perform specific administrative operations. This weakness creates a pathway for attackers who have already gained initial access to the system to potentially elevate their privileges from standard user level to administrative or system-level access. The flaw exists in the way SharePoint handles token validation and access control lists during service operations, particularly affecting the SharePoint Server 2016, 2019, and SharePoint Online environments.
The technical implementation of this vulnerability involves a specific code path within SharePoint's authentication subsystem where access control decisions are made. Attackers can exploit this by crafting specially formatted requests that bypass normal permission checks, allowing them to execute operations that should only be available to users with elevated privileges. The vulnerability is particularly concerning because it operates at the application layer and can be exploited through legitimate SharePoint web services without requiring special tools or techniques beyond understanding the SharePoint API structure. The flaw manifests when SharePoint processes requests that involve user management, site configuration changes, or administrative service calls where the system fails to properly validate the calling user's privilege level against the requested operation. This weakness aligns with CWE-284 which addresses improper access control in software systems, specifically targeting inadequate privilege validation mechanisms. The vulnerability demonstrates a classic case of insufficient authorization checking where the system assumes that authenticated users have appropriate access rights for all operations they attempt to perform.
The operational impact of this vulnerability extends beyond simple privilege escalation, as successful exploitation can lead to complete system compromise and data breaches. An attacker who successfully exploits this vulnerability can gain access to sensitive organizational data, modify or delete content, manipulate user accounts, and potentially establish persistence within the SharePoint environment. The attack vector typically involves an authenticated user who can leverage this flaw to perform administrative functions such as creating new user accounts with elevated privileges, modifying group memberships, or accessing restricted SharePoint libraries and documents. This vulnerability poses significant risk to organizations that rely heavily on SharePoint for document management, collaboration, and enterprise content management. The potential for lateral movement within the network increases substantially as attackers can use elevated privileges to access other systems or services that may share the same authentication infrastructure. From a threat actor perspective, this vulnerability provides an ideal opportunity to establish a foothold within SharePoint environments and escalate access to gain broader system control. The vulnerability's impact is further amplified by the widespread use of SharePoint across enterprise environments, making it a prime target for attackers seeking persistent access to organizational resources.
Mitigation strategies for this vulnerability require immediate implementation of Microsoft's security patches and updates, as the company released specific security updates addressing this flaw in their regular monthly patch cycle. Organizations should prioritize applying these patches to all affected SharePoint Server installations and SharePoint Online environments to prevent exploitation. Additionally, implementing network segmentation and access control measures can help limit the potential damage from successful exploitation attempts. Security administrators should review and tighten SharePoint permission policies, ensuring that users have the minimum necessary privileges for their roles. Monitoring for unusual authentication patterns or privilege escalation attempts can help detect exploitation attempts. The implementation of security controls aligned with the MITRE ATT&CK framework, specifically focusing on privilege escalation techniques, can provide additional protection layers. Organizations should also consider implementing automated vulnerability scanning tools that can identify systems running vulnerable versions of SharePoint and track patch compliance. Regular security assessments of SharePoint environments should include checks for proper access control implementation and privilege validation mechanisms to prevent similar vulnerabilities from emerging in the future.