CVE-2026-64921 in SharePoint Server
Summary
by MITRE • 08/11/2026
Missing authentication for critical function in Microsoft Office SharePoint allows an authorized attacker to elevate privileges over a network.
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Analysis
by VulDB Data Team • 08/11/2026
This vulnerability represents a critical authentication flaw within Microsoft Office SharePoint that enables authorized attackers to escalate their privileges and gain unauthorized access to sensitive functions. The issue stems from insufficient verification mechanisms that should normally validate user credentials and permissions before granting access to critical system operations. When an authenticated user can bypass these security controls, they effectively gain elevated privileges that allow them to perform actions typically restricted to administrators or users with higher clearance levels.
The technical implementation of this vulnerability involves a failure in the authorization process where SharePoint does not properly enforce access controls for privileged functions. This weakness creates an attack surface where legitimate users who have already established authentication can exploit design flaws to execute unauthorized operations. The flaw likely manifests in how the system validates user roles and permissions during critical function calls, potentially through inadequate session management or insufficient privilege checks that occur after initial authentication.
From an operational perspective, this vulnerability poses significant risks to organizations relying on SharePoint for document management, collaboration, and business-critical data storage. Attackers who can exploit this flaw can access confidential information, modify or delete critical documents, manipulate user permissions, and potentially establish persistent access to the system. The impact extends beyond immediate data compromise as attackers can use elevated privileges to move laterally within the network, escalate their access further, and conduct more sophisticated attacks against other connected systems.
The vulnerability aligns with CWE-285 which addresses improper authorization issues in software systems, specifically targeting scenarios where insufficient access controls allow unauthorized privilege escalation. From an attack framework perspective, this weakness maps to multiple ATT&CK techniques including privilege escalation through exploitation of software vulnerabilities, and potentially lateral movement as attackers use elevated privileges to access other network resources. Organizations should implement immediate mitigations including applying Microsoft security patches, implementing additional monitoring for unusual privilege usage patterns, and conducting comprehensive access control reviews.
Security teams must prioritize this vulnerability as it represents a fundamental breakdown in the security model of SharePoint systems, potentially allowing attackers with minimal initial access to achieve significant operational impact. The remediation approach requires not only patch management but also enhanced monitoring of privilege escalation attempts and validation of existing user permissions within the SharePoint environment. Organizations should also consider implementing network segmentation and principle of least privilege controls to limit the potential damage from such vulnerabilities, as the attack surface can be extended through integration with other enterprise systems that may share authentication mechanisms or user directories.