Description

IBM AIX 7.2, and 7.3 and IBM PowerVM VIOS 4.1 could allow a local attacker to overwrite critical files and obtain sensitive information due to a time-of-check to time-of-use (TOCTOU) race condition.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "7.0",
  "pubDate": "2026-08-19T20:17:04.873Z",
  "pubdate": "2026-08-19T20:17:04.873Z",
  "executiveSummary": "A time-of-check to time-of-use (TOCTOU) race condition vulnerability has been identified in IBM AIX 7.2, 7.3, and IBM PowerVM VIOS 4.1. This vulnerability arises from insecure file handling practices where a gap exists between the validation of a file's state (time-of-check) and the subsequent operation performed on that file (time-of-use).\nAn authenticated local attacker with low-level access can exploit this race condition to manipulate system operations, resulting in the unauthorized overwriting of critical system files and the potential disclosure of sensitive information.\nThe risk implications are significant, as successful exploitation could lead to privilege escalation, system integrity compromise, and unauthorized access to confidential data stored within the affected environment.\nExploitation requires local system access and precise timing to successfully interleave operations during the vulnerability window. No remote network exposure is required for this attack vector.",
  "technicalDetails": "The root cause of the vulnerability stems from a time-of-check to time-of-use (TOCTOU) race condition flaw residing within the file system interaction logic of the affected operating systems. Specifically, the vulnerable component performs a security or state validation check on a file resource and subsequently references or modifies the resource in a separate, non-atomic step.\nAffected software versions include IBM AIX 7.2, IBM AIX 7.3, and IBM PowerVM VIOS 4.1. The vulnerability does not require network exposure, as it is exclusively exploitable locally.\nAuthentication is required to access the local system environment, and the attacker must possess local execution privileges to trigger the vulnerable code paths and spawn competing processes.\nThe exploitation method relies on asynchronous execution and race condition leverage. During the execution flow, the targeted application checks the attributes, permissions, or existence of a file at the time-of-check. An attacker orchestrating a malicious local payload rapidly replaces or symlinks the targeted file with a controlled substitute prior to the time-of-use operation.\nBecause the application assumes the state verified during the check remains constant, the subsequent operation executes against the attacker-controlled resource instead of the intended file.\nPost-exploitation impact includes the ability to overwrite critical system binaries, configuration files, or data structures with arbitrary data, potentially leading to root-level compromise or denial of service. Additionally, improper file handling during these race conditions can expose sensitive information contained in restricted files to unauthorized local users."
}