# CVE-2026-34447: ONNX symlink traversal in external data loading

Source: https://junglewise.ai/threats/cve-2026-34447-onnx-symlink-traversal-in-external-data-loading  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-04-01. Updated: 2026-06-08  
License: CC BY 4.0 with a link back

CVE-2026-34447 · Severity: medium · CVSS 5.5 · Published 2026-04-01

ONNX is an open-source format for artificial intelligence models. A vulnerability in how it loads external data allows a specially crafted model file to read sensitive files from the user's computer. This could lead to the theft of private information if a user is tricked into opening a malicious AI model.

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

## Quick answers

**Is CVE-2026-34447 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-34447 being exploited in the wild.

**How severe is CVE-2026-34447?** Medium severity, with a CVSS score of 5.5, published 1 April 2026.

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

**Is there a fix for CVE-2026-34447?** 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.

**How is CVE-2026-34447 attacked?** It is attacked with local access, in a software library.

**Am I affected by CVE-2026-34447?** Check whether you run Linuxfoundation Onnx or 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"
  ```


## Technical details

A symlink traversal vulnerability exists in `onnx/onnx/checker.cc` within the `resolve_external_data_location` function. While the function attempts to validate that external data paths are relative and reside within the base directory, it uses `std::filesystem::is_regular_file`, which follows symbolic links. An attacker can provide a model where an external data reference points to a symlink within the model directory that targets a sensitive file elsewhere on the filesystem (e.g., `/etc/passwd`). When `load_external_data_for_model` is called, the library will read the contents of the linked file into the model's tensors. This is fixed in version 1.21.0.

## Affected products

- ONNX onnx < 1.21.0

## Identifiers

- CVE-2026-34447
- GHSA-p433-9wv8-28xj
- PYSEC-2026-104

## Timeline

- 2026-03-31: disclosed
- 2026-04-01: advisory
- 2026-04-01: patched: Fixed in version 1.21.0

## References

- [https://api.github.com/users/jayashwaS](https://api.github.com/users/jayashwaS)
- [https://github.com/jayashwaS](https://github.com/jayashwaS)
- [https://api.github.com/users/jayashwaS/gists%7B/gist_id%7D](https://api.github.com/users/jayashwaS/gists%7B/gist_id%7D)
- [https://api.github.com/users/jayashwaS/repos](https://api.github.com/users/jayashwaS/repos)
- [https://avatars.githubusercontent.com/u/21168815?v=4](https://avatars.githubusercontent.com/u/21168815?v=4)
- [https://api.github.com/users/jayashwaS/events%7B/privacy%7D](https://api.github.com/users/jayashwaS/events%7B/privacy%7D)

## 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)