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

> An attacker can read arbitrary files outside the intended directory via symlink path traversal in the ONNX library.

- **Severity:** High 8.7 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 1 Apr 2026
- **Updated:** 15 Jul 2026
- **Also known as:** DEBIAN-CVE-2026-27489, ECHO-bbdd-cc38-c3a7, GHSA-3r9x-f23j-gc73, PYSEC-2026-2239, UBUNTU-CVE-2026-27489

## What is CVE-2026-27489?

CVE-2026-27489 is a high-severity path traversal vulnerability in onnx, published on 1 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

Weakness: CWE-22 (Improper Limitation of a Pathname to a Restricted Directory), CWE-61 (UNIX Symbolic Link (Symlink) Following), CWE-23 (Relative Path Traversal)

## Which versions are affected by CVE-2026-27489?

3 open source packages ship an affected version, including onnx. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `onnx` | PyPI | All versions | 1.21.0 |
| `onnx` | PyPI | All versions | 1.21.0 |
| `onnx` | PyPI | All versions | 1.21.0 |

Products: Linuxfoundation Onnx.

## How do I fix CVE-2026-27489?

Upgrade onnx to 1.21.0 or later.

## Is CVE-2026-27489 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-27489 exists.

## Other vulnerabilities in onnx

- [CVE-2025-51480](https://insights.sbomify.com/CVE-2025-51480/): Path traversal in n/a (high 8.8)
- [CVE-2024-5187](https://insights.sbomify.com/CVE-2024-5187/): Arbitrary File Overwrite in download_model_with_test_data in onnx/onnx (high 8.8)
- [CVE-2026-34445](https://insights.sbomify.com/CVE-2026-34445/): ONNX: Malicious ONNX models can crash servers by exploiting unprotected object settings. (high 8.6)
- [CVE-2026-28500](https://insights.sbomify.com/CVE-2026-28500/): ONNX Untrusted Model Repository Warnings Suppressed by silent=True in onnx.hub.load() — Silent Supply-Chain Attack (high 8.6)
- [CVE-2022-25882](https://insights.sbomify.com/CVE-2022-25882/): Directory Traversal in onnx (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-27489 and fix it if it is affected.

What it is: CVE-2026-27489 is a high-severity path traversal vulnerability in onnx, published on 1 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-27489 exists.

Affected packages and fixed versions:
- onnx (PyPI): affected all versions; fixed in 1.21.0
- onnx (PyPI): affected all versions; fixed in 1.21.0
- onnx (PyPI): affected all versions; fixed in 1.21.0

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-27489/ (Markdown: https://insights.sbomify.com/CVE-2026-27489/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-27489
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-27489
- OSV: https://osv.dev/vulnerability/CVE-2026-27489

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-27489/
Summaries are generated and may contain mistakes; the official description above is the record.