A stack buffer overflow vulnerability in IBM AIX 7.2, 7.3 and IBM PowerVM VIOS 4.1 permits a remote attacker to execute arbitrary code. The flaw allows an attacker to write arbitrary data beyond the bounds of a buffer, potentially leading to full compromise of the affected system with no authentication required.

IBM AIX versions 7.2.0 through 7.3 (including all build levels <= TL04) and IBM PowerVM VIOS 4.1 (including build 4.1.0, 4.1.1, and 4.1.2) are susceptible. Service Packs for AIX (e.g., TL04SP2, TL03SP3, TL02SP5, TL05SP13) and Fix Packs for VIOS (e.g., 4.1.2.20, 4.1.1.30, 4.1.0.50) contain the remediation.

The issue carries a CVSS score of 9.8 indicating critical severity. The EPSS score is not available, which means recent data on exploit likelihood is lacking, but the absence of a KEV listing does not reduce the potential impact. Attackers would exploit the overflow through remote interfaces; successful exploitation results in arbitrary code execution with system‑wide privileges. The vulnerability is addressable via the official IBM APARs and subsequent Service Pack or Fix Pack installations, which can be applied using Live Update on AIX or post‑update procedures on VIOS. Given the critical score and the full compromise risk, this weakness is a high priority for immediate remediation.