CVE-2026-16867 in IBM
Summary
by MITRE • 08/13/2026
IBM i 7.6, 7.5, 7.4, and 7.3 could allow a remote attacker to access server resources with the privileges of an authenticated user due to improper authentication during NTLM session negotiation.
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Analysis
by VulDB Data Team • 08/13/2026
This vulnerability exists within IBM i operating systems versions 7.6, 7.5, 7.4, and 7.3, presenting a critical security risk that allows remote attackers to access server resources with the privileges of authenticated users. The flaw stems from improper authentication mechanisms during NTLM session negotiation processes, creating an avenue for unauthorized access that bypasses normal security controls. The vulnerability specifically affects systems that utilize NTLM authentication protocols, which are commonly deployed in enterprise environments for user and service authentication. Attackers can exploit this weakness to establish sessions with elevated privileges, potentially gaining access to sensitive data, system resources, or administrative functions that should only be available to authorized personnel.
The technical implementation of this vulnerability involves weaknesses in the NTLM authentication handshake process where the system fails to properly validate session credentials during negotiation phases. This misconfiguration allows attackers to manipulate authentication flows and obtain valid session tokens that grant them access equivalent to authenticated users within the system. The flaw represents a significant deviation from standard authentication protocols and can be leveraged through network-based attacks without requiring physical access or additional exploitation tools. The vulnerability is particularly concerning because it operates at the authentication layer, meaning that successful exploitation directly compromises the fundamental security controls designed to protect system resources.
From an operational impact perspective, this vulnerability creates substantial risk for organizations relying on IBM i systems for business-critical applications and data storage. Attackers who successfully exploit this weakness can potentially access confidential information, modify system configurations, or perform administrative functions that could lead to complete system compromise. The remote nature of the attack means that threat actors do not need to be physically present in the network environment, making detection more challenging and increasing the potential scope of impact. Organizations may experience data breaches, service disruptions, and compliance violations that could result in significant financial and reputational damage.
Organizations should prioritize immediate implementation of vendor-provided security patches and updates to address this vulnerability. System administrators must also implement enhanced monitoring for unusual authentication patterns and session establishment activities that could indicate exploitation attempts. Network segmentation strategies should be reinforced to limit lateral movement opportunities, while regular security assessments should verify the effectiveness of implemented controls. The vulnerability aligns with CWE-287 which addresses improper authentication issues in software systems, and represents a potential entry point for tactics categorized under ATT&CK technique T1078 for valid accounts and T1566 for social engineering attacks. Additional defensive measures including multi-factor authentication implementation, regular credential rotation, and comprehensive access control reviews should be implemented as part of a layered security approach to reduce the overall risk exposure associated with this authentication bypass vulnerability.