CVE-2026-49114: Linuxfoundation Onnx

High severity, CVSS 7.1. EPSS: 0.2% chance of exploitation in the next 30 days.

In ONNX before 1.21.0, the 'save_external_data' function builds the external-data file path from the model's external_data location field and opens it for writing without 'O_NOFOLLOW/O_EXCL', after a non-atomic 'os.path.isfile()' check. A local attacker with write access to the directory where a victim serializes external data can deterministically pre-plant a symlink that is being followed, causing the victim's write to append to any file the victim can write, e.g. ~/.ssh/authorized_keys, cron files, or application configs. Fixed in 1.21.0.

Affected products

• Linuxfoundation Onnx: before 1.21.0 (fixed in 1.21.0)

Published 2026-08-21. Last modified 2026-09-16.