CVE-2026-16896 in IBM
Summary
by MITRE • 08/13/2026
IBM i 7.6, 7.5, 7.4, and 7.3 could allow a local authenticated attacker to obtain unauthorized access to files due to a time-of-check time-of-use (TOCTOU) race condition.
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Analysis
by VulDB Data Team • 08/13/2026
This vulnerability represents a critical time-of-check time-of-use race condition flaw affecting IBM i operating systems version 7.6, 7.5, 7.4, and 7.3. The vulnerability stems from improper synchronization between file access checks and actual file operations, creating a window where an attacker can manipulate system state between the moment when access permissions are verified and when the operation is executed. This fundamental flaw allows local authenticated users to exploit the temporal gap in security validation mechanisms.
The technical implementation of this vulnerability involves the operating system's file access control subsystem where file permission checks occur before actual file operations take place. During this brief interval, an attacker can modify file permissions, replace files, or alter directory structures to gain unauthorized access to resources that should otherwise be restricted. The race condition typically manifests when a process performs a permission check on a file or directory and subsequently accesses the same resource without revalidating permissions, allowing malicious actors to manipulate the target between these two operations.
From an operational impact perspective, this vulnerability compromises the integrity of IBM i's access control mechanisms and can lead to unauthorized data access, privilege escalation, and potential system compromise. Local authenticated attackers who already possess valid login credentials can leverage this flaw to bypass file-level security controls, potentially accessing sensitive system files, user data, or administrative resources that should be protected from their current permission level. The attack vector requires only local system access and authentication, making it particularly dangerous in environments where multiple users share systems or where privilege separation is critical.
The vulnerability aligns with CWE-367, which specifically addresses time-of-check to time-of-use race conditions, and maps to several ATT&CK techniques including privilege escalation through access token manipulation and credential access through file system permissions. Organizations should implement immediate mitigations including applying the latest IBM security patches, reviewing system configurations for unnecessary local accounts, implementing robust monitoring for suspicious file access patterns, and conducting thorough security assessments of file access controls. Additionally, system administrators should consider implementing additional security measures such as file integrity monitoring solutions and enhanced logging of file access operations to detect potential exploitation attempts.