CVE-2026-16875 in AIX
Summary
by MITRE • 08/19/2026
IBM AIX 7.2, and 7.3 and IBM PowerVM VIOS 4.1 could allow a local attacker to execute arbitrary commands due to shell metacharacter injection.
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Analysis
by VulDB Data Team • 08/20/2026
The vulnerability identified in IBM AIX versions 7.2 and 7.3, as well as IBM PowerVM Virtual I/O Server (VIOS) version 4.1, represents a critical security flaw rooted in improper input validation within system utilities or administrative interfaces. This specific weakness allows for shell metacharacter injection, which is a subset of command injection vulnerabilities where an attacker exploits the interpretation of special characters by the operating system's command interpreter to execute unintended commands. The core technical issue lies in the failure to properly sanitize user-supplied data before it is passed to underlying system calls or scripts that invoke a shell environment such as /bin/sh or ksh. When input containing metacharacters like semicolons, pipes, ampersands, or backticks is not adequately escaped or validated, these characters are interpreted by the shell rather than treated as literal data, thereby altering the structure of the intended command and enabling the execution of arbitrary code.
From a technical perspective, this flaw typically manifests in scenarios where administrative tools accept input from local users to perform system configuration tasks, manage virtual machines, or query hardware status. If these tools construct commands dynamically by concatenating user input with static strings without rigorous validation, an attacker can inject malicious payloads. For instance, if a tool accepts a hostname or file path as input and passes it directly to a shell command for processing, an adversary could append additional commands using semicolons or logical operators. This capability is particularly dangerous in the context of IBM PowerVM VIOS, which serves as the hypervisor layer managing virtualized resources on POWER systems. A successful exploitation here does not merely compromise a single application but potentially grants control over critical infrastructure components that manage network interfaces, storage volumes, and partition configurations for multiple guest operating systems running atop the VIOS instance.
The operational impact of this vulnerability is severe due to its local nature combined with high privilege escalation potential. Although the initial attack vector requires local access, meaning an attacker must first authenticate or gain a foothold on the system through other means such as phishing, weak credentials, or exploiting another lower-severity flaw, the subsequent ability to execute arbitrary commands effectively bypasses all remaining security controls within that context. If exploited by a user with administrative privileges, which is common in AIX and VIOS environments where root access is frequently required for maintenance tasks, the attacker gains full control over the operating system. This can lead to complete data exfiltration, modification of critical configuration files, installation of persistent backdoors, or use of the compromised host as a pivot point to attack other systems within the network. In the case of VIOS 4.1, compromising the hypervisor layer could potentially impact the availability and integrity of all virtual machines hosted on that physical server, leading to significant business disruption.
This vulnerability aligns with Common Weakness Enumeration (CWE) category CWE-78 Improper Neutralization of Special Elements used in an OS Command, commonly known as OS Command Injection. It also maps to MITRE ATT&CK technique T1059 Command and Scripting Interpreter, specifically sub-techniques involving shell commands such as sh or ksh on Unix-like systems. The exploitation path typically involves the attacker crafting a payload that exploits the lack of input sanitization, sending it through an interface that processes system-level operations. Defense in depth strategies are essential to mitigate this risk. Organizations should ensure that all applicable IBM security patches and maintenance levels for AIX 7.2, 7.3, and PowerVM VIOS 4.1 are promptly applied, as vendors typically release fixes that implement proper input validation or restrict the use of shell interpreters in affected utilities. Additionally, implementing strict least-privilege principles can limit the blast radius if an account is compromised by ensuring that users do not possess unnecessary administrative rights. Network segmentation and monitoring for anomalous command execution patterns using host-based intrusion detection systems further enhance resilience against such exploitation attempts.