CVE-2026-56168
Summary
by MITRE • 07/14/2026
Null pointer dereference in Windows SMB Server allows an authorized attacker to deny service over a network.
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Analysis
by VulDB Data Team • 07/14/2026
A null pointer dereference vulnerability in the Windows Server Message Block SMB server implementation represents a critical security flaw that can be exploited by authorized attackers to execute denial of service attacks across network boundaries. This vulnerability stems from improper validation of pointer references within the SMB server component, specifically when processing certain network requests that contain malformed or unexpected data structures. The flaw exists at the protocol handling layer where the system attempts to dereference a null pointer during normal SMB operation sequences, leading to abrupt process termination and service unavailability.
The technical nature of this vulnerability aligns with CWE-476 which defines null pointer dereference as a condition where a program attempts to access memory through a null reference, typically resulting in application crashes or system instability. When an authorized attacker sends specifically crafted SMB requests to a vulnerable Windows system, the server processes these packets and encounters a scenario where a required pointer variable remains uninitialized or explicitly set to null. During subsequent operations, the system attempts to access memory through this null reference causing an immediate crash of the SMB service or entire system process responsible for handling network file sharing operations.
The operational impact of this vulnerability extends beyond simple service disruption as it can be weaponized to create persistent denial of service conditions that affect critical business operations relying on Windows file sharing capabilities. Network administrators may experience cascading failures when multiple systems become unavailable simultaneously, particularly in enterprise environments where SMB is heavily utilized for file server operations and shared resource access. Attackers can leverage this vulnerability through various network access points including wireless networks, remote desktop connections, or direct network interfaces, making the attack surface broad and difficult to monitor effectively.
This vulnerability directly relates to ATT&CK technique T1499 which encompasses network denial of service attacks targeting system availability. The exploitation process typically involves sending specially crafted SMB packets that trigger the null pointer dereference condition, requiring minimal privileges since the attacker only needs authorized access to the network or system. Mitigation strategies should include immediate deployment of Microsoft security patches addressing the specific SMB server vulnerability, implementation of network segmentation to limit attack vectors, and enhanced monitoring of SMB traffic for anomalous patterns indicating potential exploitation attempts. Additional defensive measures encompass disabling unnecessary SMB versions, implementing strict firewall rules controlling SMB port access, and establishing robust intrusion detection systems capable of identifying malicious SMB request patterns that could indicate exploitation attempts.