CVE-2026-49114
High
Description
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.
SeverityHigh
CVSS7.1
Exploit probability—
ProductLinuxfoundation Onnx
PublishedAug 21, 2026
First seenAug 21, 2026
How to fix
Update
- linuxfoundation onnx1.21.0 or later
- onnx1.21.0 or later
Vendor advisories
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| linuxfoundation onnx | v < 1.21.0 | 1.21.0 |
| onnxPyPI | v < 1.21.0 | 1.21.0 |
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