---
id: CVE-2026-34446
aliases:
  - GHSA-cmw6-hcpp-c6jp
  - PYSEC-2026-2241
title: 'ONNX: Arbitrary File Read via ExternalData Hardlink Bypass in ONNX load'
summary: 'ONNX: Arbitrary File Read via ExternalData Hardlink Bypass in ONNX load'
severity: medium
cvss: 4.7
cvssVector: 'CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:H/I:N/A:N'
vendor: onnx
product: onnx
ecosystem: pip
affected:
  - onnx < 1.21.0
patched:
  - onnx 1.21.0
published: '2026-04-01'
updated: '2026-09-10'
sourceUpdated: '2026-09-10T03:50:43.899271555Z'
source: OSV
sourceUrl: 'https://osv.dev/vulnerability/GHSA-cmw6-hcpp-c6jp'
references:
  - url: 'https://github.com/onnx/onnx/security/advisories/GHSA-cmw6-hcpp-c6jp'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-34446'
  - url: >-
      https://github.com/onnx/onnx/commit/4755f8053928dce18a61db8fec71b69c74f786cb
  - url: 'https://github.com/onnx/onnx'
tags:
  - osv
  - pip
epss: 0.00171
epssPercentile: 0.05691
ingestedAt: '2026-07-13T18:57:56.746Z'
---

## Overview

### Summary
The issue is in `onnx.load` — the code checks for symlinks to prevent path traversal, but completely misses hardlinks, which is the problem, since a hardlink looks exactly like a regular file on the filesystem.

### The Real Problem
The validator in `onnx/checker.cc` only calls `is_symlink()` and never checks the inode or `st_nlink`, so a hardlink walks right through every security check without any issues.

### Impact
Especially dangerous in AI supply chain scenarios like HuggingFace — a single malicious model is enough to silently steal secrets from the victim's machine without them noticing anything.

## Affected packages

- `onnx < 1.21.0`

## Remediation

Upgrade to a patched release:

- `onnx 1.21.0`