CVE-2026-56401 in Wazuh
Summary
by MITRE • 07/08/2026
Wazuh wazuh-modulesd before 5.0.0-beta3 contains a null pointer dereference vulnerability in inventory_sync FlatBuffer DataValue handling. An enrolled agent can send a verifier-valid DataValue message omitting the optional id field, causing wazuh-modulesd to crash when dereferencing data->id()->string_view() without null validation, resulting in denial of service.
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Analysis
by VulDB Data Team • 07/08/2026
This vulnerability exists within the Wazuh wazuh-modulesd component prior to version 5.0.0-beta3 and represents a critical null pointer dereference flaw that can lead to remote denial of service conditions. The issue specifically manifests during inventory synchronization processes when handling FlatBuffer DataValue messages, where the system fails to properly validate the presence of optional fields before attempting to access them. The vulnerability stems from the absence of null checks when processing verifier-valid DataValue messages that omit the optional id field, creating a scenario where data->id()->string_view() is invoked on a null pointer reference.
The technical implementation of this flaw occurs within the inventory_sync functionality of wazuh-modulesd, which processes incoming DataValue messages from enrolled agents. When an agent sends a message without including the optional id field, the system assumes the presence of this field and attempts to dereference it directly through data->id()->string_view() method calls. This pattern violates fundamental defensive programming principles and creates an execution path where a null pointer exception occurs, leading to immediate process termination and system crash. The vulnerability is classified as CWE-476 Null Pointer Dereference, which represents one of the most common and dangerous classes of software defects in systems handling external data inputs.
The operational impact of this vulnerability extends beyond simple service disruption as it creates a potential attack vector for adversaries seeking to compromise Wazuh monitoring infrastructure. An authenticated attacker with access to an enrolled agent can exploit this weakness to repeatedly crash wazuh-modulesd processes, effectively rendering the system unable to perform inventory synchronization tasks and potentially disrupting broader security monitoring capabilities. This denial of service condition directly impacts the availability aspect of the CIA triad, as it prevents legitimate users from accessing critical system inventory data and functionality. The attack requires minimal privileges since it only necessitates access to an enrolled agent, making it particularly dangerous in environments where agent compromise is possible.
Mitigation strategies for this vulnerability include immediate deployment of Wazuh version 5.0.0-beta3 or later, which implements proper null validation checks before accessing the id field. Organizations should also implement network segmentation and access controls to limit agent enrollment to trusted systems only, reducing the attack surface available to potential adversaries. Additionally, monitoring systems should be configured to detect repeated wazuh-modulesd crashes or restarts that may indicate exploitation attempts. From a defensive perspective, this vulnerability aligns with ATT&CK technique T1499.004 Network Denial of Service, as it specifically targets system availability through process termination. Security teams should also consider implementing automated incident response procedures to quickly detect and contain exploitation attempts, while maintaining regular patching schedules to address similar vulnerabilities in the broader Wazuh ecosystem.