Time-of-check Time-of-use (TOCTOU) Race Condition in onnx - #VU128171
Published: April 27, 2026
Vulnerability identifier: #VU128171
CSH Severity: High
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Amber
CVE-ID: N/A
CWE-ID: CWE-367
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: Open Neural Network Exchange
Affected software:
onnx
onnx
Detailed vulnerability description
The vulnerability allows a remote attacker to overwrite arbitrary files.
The vulnerability exists due to time-of-check time-of-use race condition in save_external_data in onnx.external_data_helper.py when saving external tensor data to an external file. A remote attacker can replace the target file with a symlink to overwrite arbitrary files.
User interaction is required to save or re-save a model with external data.
Remediation
Install security update from vendor's website.