CVE-2026-56157 in SharePoint Server
Summary
by MITRE • 07/14/2026
Improper access control in Microsoft Office SharePoint allows an authorized attacker to perform spoofing over a network.
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Analysis
by VulDB Data Team • 07/15/2026
This vulnerability represents a critical weakness in Microsoft Office SharePoint's access control mechanisms that enables authenticated attackers to conduct network-based spoofing attacks. The flaw stems from insufficient validation of user permissions and session management within the SharePoint infrastructure, allowing malicious actors who have gained initial access to the system to manipulate network traffic and impersonate legitimate users or services. The vulnerability typically manifests when the platform fails to properly authenticate network requests or validate the integrity of communication channels between clients and servers.
The technical implementation of this weakness occurs at multiple levels within the SharePoint architecture where access control decisions are made. Attackers can exploit this by leveraging their authorized status to manipulate session tokens, cookies, or authentication headers that should normally be protected from modification. When proper access controls are bypassed, an attacker can intercept network communications and inject forged requests that appear legitimate to the SharePoint server. This creates opportunities for man-in-the-middle attacks where the malicious actor can redirect traffic, modify content, or impersonate other users within the system.
The operational impact of this vulnerability extends beyond simple unauthorized access as it fundamentally compromises the integrity of the communication channel between SharePoint components and external systems. Network spoofing enabled by improper access control allows attackers to manipulate data flows, potentially leading to data exfiltration, privilege escalation, or complete system compromise. Organizations may experience unauthorized modifications to SharePoint content, unauthorized access to sensitive documents, or disruption of business-critical collaboration services that depend on the platform's security assurances.
Security mitigations for this vulnerability should focus on strengthening authentication mechanisms and implementing robust network monitoring solutions. Organizations must ensure proper session management with secure token generation and validation processes, implement network segmentation to limit attack surface, and deploy intrusion detection systems capable of identifying suspicious traffic patterns associated with spoofing attempts. Regular security assessments should verify that access control policies are properly enforced and that network communications are adequately protected through encryption and integrity checking mechanisms.
This vulnerability aligns with CWE-285 which addresses improper authorization in software systems, specifically targeting the failure to properly enforce access controls on network resources. The attack vector corresponds to techniques described in MITRE ATT&CK framework under T1071.004 for application layer protocols and T1566 for spoofing attacks. Organizations should implement defense-in-depth strategies that include network traffic analysis, proper access control configuration, regular security updates, and employee training to recognize potential social engineering components that might facilitate initial access to the SharePoint environment.