Description

IBM AIX 7.2, and 7.3 and IBM PowerVM VIOS 4.1 could allow a local attacker to gain elevated privileges due to a format string vulnerability.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "7.0",
  "pubDate": "2026-08-28T22:16:46.310Z",
  "pubdate": "2026-08-28T22:16:46.310Z",
  "executiveSummary": "A critical format string vulnerability exists within IBM AIX 7.2, 7.3, and IBM PowerVM VIOS 4.1, which may permit a local attacker to execute arbitrary code or escalate privileges.\nThis vulnerability stems from improper validation of user-supplied input when passed to format-handling functions in sensitive system components.\nThe flaw allows an authenticated local user to manipulate the internal state of a process, potentially leading to unauthorized system control.\nThe risk implication is significant as it provides a vector for privilege escalation, effectively bypassing standard security boundaries within the affected OS environments.\nSuccessful exploitation requires local access, but does not necessitate interaction with remote network services, limiting the attack surface to existing system users.",
  "technicalDetails": "The vulnerability is characterized as a classic format string bug where user-controlled input is used directly as the format argument in functions belonging to the printf() family, such as sprintf(), vsnprintf(), or syslog().\nIn the affected versions of IBM AIX and PowerVM VIOS, the root cause is the failure to sanitize input buffers before they are processed by these variadic functions.\nWhen an attacker provides a string containing format specifiers like %x, %p, or %n, the vulnerable function interprets these tokens as instructions rather than literal data. Specifically, the %n specifier is particularly dangerous as it allows for memory writes to arbitrary addresses defined by the arguments on the stack.\nThe attack flow commences with the adversary identifying a setuid binary or a privileged system service that accepts user input—such as command-line arguments, environment variables, or configuration file content—which is subsequently passed to a vulnerable format function without proper delimiters.\nBy crafting a malicious payload, the attacker can leak sensitive information from the stack by traversing pointer offsets using format specifiers, or perform a write-what-where primitive to overwrite critical memory regions, such as the Global Offset Table (GOT), return addresses on the stack, or function pointers.\nBy overwriting a function pointer, an attacker can redirect the execution flow to a custom payload (e.g., shellcode) or invoke existing system functions like setuid(0) followed by execve('/bin/sh') to achieve root or equivalent administrative privileges.\nBecause AIX and VIOS rely heavily on these internal system calls for resource management and device virtualization, the compromise of a component within this architecture can lead to complete system takeover, including the ability to bypass the restricted shell environment typical of VIOS.\nThe vulnerability necessitates local access, meaning the attacker must already be logged into the target environment, whether through a standard user session or a restricted CLI interface in the case of VIOS. Once the memory corruption occurs, the attacker gains the execution context of the vulnerable process, which often possesses elevated system permissions."
}