CVE-2026-18822 in AIX
Summary
by MITRE • 08/21/2026
IBM AIX 7.2, and 7.3 and IBM PowerVM VIOS 4.1 could allow a local attacker to cause a denial of service due to uncontrolled resource consumption when parsing directory records.
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Analysis
by VulDB Data Team • 08/21/2026
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 significant risk related to local denial of service through uncontrolled resource consumption. This flaw is rooted in the handling of directory records during parsing operations within the operating system's core components or associated virtualization management layers. When a local attacker interacts with these systems by providing specifically crafted input intended for directory record processing, the software fails to properly validate or limit the resources allocated for this task. The lack of adequate bounds checking or resource caps allows an unprivileged user to trigger excessive memory allocation, CPU cycles, or file descriptor usage, leading to system instability or complete service interruption.
From a technical perspective, this issue aligns with CWE-400, which describes Uncontrolled Resource Consumption. In the context of AIX and PowerVM VIOS, the parsing mechanism likely processes directory entries without sufficient scrutiny regarding their size, complexity, or quantity. An attacker can exploit this by creating directories containing an excessive number of records or records with malformed attributes that force the parser into a loop or recursive state that consumes system resources disproportionately to normal operations. Because the vulnerability requires local access, it typically involves a user account on the system rather than remote network exploitation, though social engineering or prior compromise may be necessary for initial foothold acquisition.
The operational impact of this vulnerability is primarily centered around availability and reliability. A successful exploit can lead to resource exhaustion that degrades performance for all users sharing the same environment or causes the affected service or entire host to become unresponsive. In a virtualized infrastructure managed by PowerVM VIOS, such instability could potentially affect multiple logical partitions if the underlying hypervisor resources are impacted. This results in downtime, loss of productivity, and potential data integrity issues if processes are abruptly terminated due to resource limits being hit. For enterprise environments relying on AIX for critical workloads, this poses a risk to service level agreements and operational continuity.
This vulnerability maps directly to MITRE ATT&CK technique T1499, Endpoint Denial of Service, specifically under the sub-technique of Resource Exhaustion: Oscillating Overhead or Resource Starvation. It also relates to CWE-787, Out-of-bounds Write, if the parsing error leads to memory corruption that crashes the process, although the primary description emphasizes resource consumption rather than code execution. The attack vector is classified as Local (L), requiring physical or logical access to the system before exploitation can occur. This limits the blast radius compared to remote vulnerabilities but remains critical for securing multi-tenant environments and systems with multiple user accounts where privilege escalation might follow a successful denial of service event by triggering automatic restarts that expose other weaknesses.
Mitigation strategies should focus on both immediate patching and long-term architectural controls. IBM has released updates addressing this issue, so applying the latest security patches to AIX 7.2, 7.3, and PowerVM VIOS 4.1 is the primary remediation step. Administrators must ensure that their maintenance windows include these specific fixes to close the gap in resource validation logic. Beyond patching, implementing strict user quotas and resource limits via tools like chroot environments or containerization can isolate potential impacts. Additionally, monitoring system metrics for unusual spikes in CPU or memory usage associated with directory operations can help detect attempted exploitation early. Regular audits of local accounts and enforcement of least privilege principles reduce the number of users capable of triggering this vulnerability, thereby lowering the overall risk profile of the infrastructure.