# CVE-2026-34446: ONNX: Arbitrary File Read via ExternalData Hardlink Bypass in ONNX load

Source: https://junglewise.ai/threats/cve-2026-34446-onnx-arbitrary-file-read-via-externaldata-hardlink-bypass-in-onnx  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-04-01  
License: CC BY 4.0 with a link back

CVE-2026-34446 · Severity: low · CVSS 3.1 · Published 2026-04-01

Open Neural Network Exchange (ONNX) is an open standard for machine learning interoperability. Prior to version 1.21.0, there is an issue in onnx.load, the code checks for symlinks to prevent path traversal, but completely misses hardlinks because a hardlink looks exactly like a regular file on the filesystem. This issue has been patched in version 1.21.0.

Technologies: [onnx (PyPI)](https://junglewise.ai/threats/technologies/onnx). Vendors: [PyPI](https://junglewise.ai/threats/vendors/pypi).

## Quick answers

**Is CVE-2026-34446 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-34446 being exploited in the wild.

**How severe is CVE-2026-34446?** Low severity, with a CVSS score of 3.1, published 1 April 2026.

**Which products and versions are affected?** onnx (PyPI) ECOSYSTEM:introduced=0,fixed=1.21.0.

**Is there a fix for CVE-2026-34446?** Yes. onnx (PyPI): upgrade to 1.21.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**Am I affected by CVE-2026-34446?** Check whether you run onnx (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- onnx (PyPI): upgrade to 1.21.0 or later

  ```sh
  pip install "onnx>=1.21.0"
  ```


## Affected products

- onnx (PyPI) ECOSYSTEM:introduced=0,fixed=1.21.0

## Identifiers

- CVE-2026-34446
- GHSA-cmw6-hcpp-c6jp
- PYSEC-2026-2241

## Related threats

- [ONNX memory exhaustion in packed tensor unpacking](https://junglewise.ai/threats/cve-2026-115922-open-neural-network-exchange-onnx-is-an-open-standard-for)
- [ONNX null pointer dereference in shape inference](https://junglewise.ai/threats/cve-2026-115921-open-neural-network-exchange-onnx-is-an-open-standard-for)
- [ONNX ConvTranspose shape inference denial of service](https://junglewise.ai/threats/cve-2026-115920-open-neural-network-exchange-onnx-is-an-open-standard-for)
- [ONNX out-of-bounds read in RNN shape inference](https://junglewise.ai/threats/cve-2026-115919-open-neural-network-exchange-onnx-is-an-open-standard-for)
- [ONNX TOCTOU race condition in save_external_data](https://junglewise.ai/threats/onnx-toctou-race-condition-in-save-external-data-b85422b8)