CVE-2026-16848 in AIX
Summary
by MITRE • 08/19/2026
IBM AIX 7.2, and 7.3 and IBM PowerVM VIOS 4.1 could allow a remote attacker to execute arbitrary commands due to improper neutralization of shell metacharacters in DHCP options.
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Analysis
by VulDB Data Team • 08/19/2026
The vulnerability identified involves a critical flaw within the Dynamic Host Configuration Protocol (DHCP) client implementation found in specific versions of IBM AIX, namely 7.2 and 7.3, as well as IBM PowerVM VIOS version 4.1. This security issue stems from an improper neutralization of shell metacharacters when processing DHCP options received from a network server. In standard operating system operations, the DHCP client is responsible for retrieving configuration parameters such as IP addresses, subnet masks, and default gateways from a DHCP server to configure the local network interface automatically. The core technical flaw lies in how these retrieved option values are handled internally by the AIX networking stack before being passed to underlying shell utilities or command interpreters for application.
Specifically, when the system processes certain DHCP options that contain user-controllable input, it fails to adequately sanitize special characters such as semicolons, pipes, ampersands, and backticks. These metacharacters hold significant meaning in Unix-like shells, allowing for command chaining, redirection, and execution of arbitrary programs. Because the validation logic is insufficient, a malicious actor operating on the same network segment can craft a rogue DHCP server or manipulate existing DHCP traffic to inject these shell metacharacters into specific option fields. When the vulnerable AIX or VIOS system processes this malformed data, it inadvertently passes the unsanitized input directly to a command interpreter without proper escaping or filtering mechanisms in place.
This architectural weakness results in Remote Code Execution (RCE), allowing an attacker who can send packets to the affected system on port 67 or 68 to execute arbitrary commands with the privileges of the user running the DHCP client process, which is typically root or a highly privileged service account. The operational impact of this vulnerability is severe, as it grants full control over the compromised host. An attacker could use this access to install malware, create backdoors, exfiltrate sensitive data, pivot further into the internal network by leveraging the compromised system as a foothold, or disrupt critical services hosted on AIX and PowerVM infrastructure. Given that IBM AIX is often deployed in enterprise environments for mission-critical workloads, such an intrusion can lead to significant business disruption and compliance violations.
From a classification perspective, this vulnerability aligns with CWE-78, which describes Improper Neutralization of Special Elements used in an OS Command, commonly known as OS Command Injection. The attack vector is categorized under the MITRE ATT&CK framework technique T1059, specifically sub-technique 004 for Unix Shell Commands, indicating that the attacker leverages native system utilities to execute malicious payloads remotely via network interaction rather than local access or physical tampering.
Mitigation strategies must focus on both immediate remediation and long-term architectural hardening. The primary defense is to apply the latest security patches provided by IBM as soon as they become available for AIX 7.2, 7.3, and PowerVM VIOS 4.1. These updates typically include code changes that enforce strict input validation and proper escaping of special characters within DHCP option processing routines. In environments where patching is not immediately feasible, network segmentation should be implemented to restrict access to DHCP servers only from trusted subnets or specific authorized devices. Additionally, deploying Intrusion Detection Systems (IDS) capable of detecting anomalous DHCP traffic patterns can help identify attempts to exploit this vulnerability in real-time. Administrators should also audit their DHCP server configurations to ensure that dynamic updates are restricted and that rogue DHCP servers cannot easily operate within the network perimeter without detection.