CVE-2026-18101 in IBM
Summary
by MITRE • 08/13/2026
IBM i 7.6, 7.5, 7.4, and 7.3 could allow a local attacker to gain elevated privileges due to improper management of thread authority swaps.
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Analysis
by VulDB Data Team • 08/13/2026
This vulnerability exists within IBM i operating systems across versions 7.3 through 7.6, presenting a critical privilege escalation risk for local attackers. The flaw stems from inadequate handling of thread authority swaps, which occurs when the system transitions between different security contexts during thread execution. When threads switch between user and system authorities, the operating system fails to properly validate or enforce access controls, creating opportunities for malicious code to exploit these transitions and elevate privileges beyond normal operational boundaries.
The technical implementation of this vulnerability involves the improper management of authority levels during concurrent thread execution within the IBM i environment. When threads perform operations that require context switching between different privilege levels, the system's authorization mechanisms do not adequately verify that the transitioning thread maintains appropriate clearance for the target operation. This mismanagement allows an attacker with local access to manipulate thread execution flows and potentially execute code with elevated privileges, effectively bypassing standard security controls that should prevent such escalation.
From an operational impact perspective, this vulnerability represents a severe threat to IBM i system integrity and data protection. Local attackers who can leverage this flaw gain the ability to execute arbitrary commands with system-level privileges, potentially leading to complete system compromise. The attack surface is particularly concerning because it requires only local access, meaning that any user with login credentials to the system could exploit this vulnerability. This makes the risk particularly high in environments where multiple users have local access or where account credentials may be compromised through social engineering or other attack vectors.
The vulnerability maps directly to CWE-284 Access Control flaws and specifically relates to improper privilege management within multi-threaded environments. According to ATT&CK framework, this represents a privilege escalation technique under T1068, where adversaries leverage weaknesses in system authorization mechanisms to gain higher-level permissions. Organizations running affected IBM i versions should immediately apply the relevant security patches provided by IBM to address this vulnerability. Additionally, implementing comprehensive monitoring for unusual thread behavior and authority transitions can help detect potential exploitation attempts. System administrators should also consider restricting local access where possible and ensuring that all users maintain only the minimum necessary privileges required for their operational functions.
The root cause analysis reveals that IBM i's thread management subsystem fails to properly enforce mandatory access controls during context switches, creating a window where unauthorized privilege escalation can occur. This weakness is particularly dangerous because it operates at the kernel level within the operating system, making detection and prevention extremely challenging once exploitation has occurred. The vulnerability demonstrates a fundamental flaw in how IBM i handles concurrent execution contexts, where the security model assumes proper authority management but fails to validate these assumptions during actual runtime operations.
Security professionals should recognize this vulnerability as part of broader patterns affecting multi-threaded operating systems where context switching mechanisms create potential attack vectors for privilege escalation. The complexity of IBM i's security architecture means that exploitation may require specific conditions and timing, but the potential impact remains severe enough to warrant immediate attention. Organizations should conduct thorough risk assessments to determine their exposure levels and implement layered defensive measures including network segmentation, access control reviews, and continuous monitoring of system logs for evidence of unauthorized privilege escalation attempts.
IBM i administrators must understand that this vulnerability affects not just individual systems but potentially entire enterprise environments where multiple IBM i systems may be interconnected. The exploitation of such flaws can lead to cascading security incidents where compromised systems serve as launching points for attacks against other connected systems. Regular security assessments and vulnerability scanning should include specific checks for thread authority management issues, as these vulnerabilities often remain undetected until actively exploited in real-world scenarios. The remediation process requires careful attention to ensure that security patches do not introduce compatibility issues with existing applications or system configurations.