CVE-2026-28500: Onnx ONNX Untrusted Model Repository Warnings Vulnerability

HIGH
Advisory Identifier: GHSA-hqmj-h5c6-369m
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CVSS 8.6
CWE-494 CWE-693 CWE-345
Published
Advisory Summary

CVE-2026-28500 is a HIGH (CVSS 8.6) onnx untrusted model repository warnings vulnerability (CWE-494: Download of Code Without Integrity Check) affecting Onnx libraries in the PyPI ecosystem. The issue involves onnx untrusted model repository warnings suppressed by silent=true in onnx.hub.load() — silent supply-chain attack. Remediation is available by upgrading affected packages to version 1.21.0rc1.

CVE-2026-28500 at a Glance

CVE Identifier CVE-2026-28500
GHSA Identifier GHSA-hqmj-h5c6-369m
Severity HIGH
CVSS v3.1 Base Score 8.6
CWE Classification CWE-494: Download of Code Without Integrity Check
Affected Product Onnx
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 8.6

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Changed (S:C)
Confidentiality High (C:H)
Integrity None (I:N)
Availability None (A:N)

How to Fix CVE-2026-28500

To remediate this vulnerability, upgrade all affected Onnx dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

onnx fixed: 1.21.0rc1 
pip install onnx>=1.21.0rc1
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

pip show onnx

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2026-28500, inspect your installed packages using pip:

pip show onnx

Analyze the terminal output to locate any version of Onnx in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 1.21.0rc1), your application is affected.

Note: The pip show onnx command checks currently installed packages in your active Python environment.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-494: Download of Code Without Integrity Check, where the product downloads source code or an executable from a remote location and executes the code without sufficiently verifying the origin and integrity of the code. In Onnx, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

## What's the issue Passing `silent=True` to `onnx.hub.load()` kills all trust warnings and user prompts. This means a model can be downloaded from any unverified GitHub repo with zero user awareness. ```python if not _verify_repo_ref(repo) and not silent: # completely skipped when silent=True print("The model repo... is not trusted") if input().lower() != "y": return None ``` On top of that, the SHA256 integrity check is useless here — it validates against a manifest that lives in the same repo the attacker controls, so the hash will always match. ## Impact Any pipeline using `hub.load()` with `silent=True` and an external repo string is silently loading whatever the repo owner ships. If that model executes arbitrary code on load, the attacker has access to the machine. ## Resolved by removing the feature ## References - [Write-up](https://github.com/ZeroXJacks/CVEs/blob/main/2026/CVE-2026-28500.md)

CVE-2026-28500 Affected Onnx Versions

1 component(s)
Fixed Versions:
1.21.0rc1
Product / Package Ecosystem Affected Versions Fixed Version
onnx
pypi/onnx
PyPI
< 1.21.0rc1
1.21.0rc1

References

GitHub Advisory / Wiki ADVISORY
https://github.com/onnx/onnx/security/advisories/GHSA-hqmj-h5c6-369m
NVD — CVE-2026-28500 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-28500
Onnx Source Repository REPOSITORY
https://github.com/ZeroXJacks/CVEs/blob/main/2026/CVE-2026-28500.md
Onnx Source Repository REPOSITORY
https://github.com/onnx/onnx
Onnx Source Repository REPOSITORY
https://github.com/pypa/advisory-database/tree/main/vulns/onnx/PYSEC-2026-103.yaml

Frequently Asked Questions

What is CVE-2026-28500?
CVE-2026-28500 is a security vulnerability in Onnx involving ONNX Untrusted Model Repository Warnings Suppressed by silent=True in onnx.hub.load() — Silent Supply-Chain Attack under CWE-494: Download of Code Without Integrity Check.
Which Onnx versions are affected?
Affected versions include releases prior to 1.21.0rc1 across affected packages: onnx.
What version fixes CVE-2026-28500?
Upgrading to 1.21.0rc1 (or the latest patched release for your respective branch) resolves the vulnerability.
Is onnx affected?
Yes, onnx is affected in releases prior to 1.21.0rc1. Upgrade your dependency to 1.21.0rc1 or later.
What is the CVSS score of CVE-2026-28500?
CVE-2026-28500 has a CVSS v3.1 base score of 8.6 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N.
What CWE is associated with CVE-2026-28500?
CVE-2026-28500 is classified under CWE-494: Download of Code Without Integrity Check (The product downloads source code or an executable from a remote location and executes the code without sufficiently verifying the origin and integrity of the code.).
How can I check PyPI dependencies for CVE-2026-28500?
Run the dependency tree command: 'pip show onnx'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-hqmj-h5c6-369m",
  "modified" : "2026-06-08T18:35:09Z",
  "published" : "2026-03-16T16:23:28Z",
  "aliases" : [ "CVE-2026-28500" ],
  "summary" : "ONNX Untrusted Model Repository Warnings Suppressed by silent=True in onnx.hub.load() — Silent Supply-Chain Attack",
  "details" : "## What's the issue\nPassing `silent=True` to `onnx.hub.load()` kills all trust warnings and user prompts. This means a model can be downloaded from any unverified GitHub repo with zero user awareness.\n \n```python\nif not _verify_repo_ref(repo) and not silent:\n    # completely skipped when silent=True\n    print(\"The model repo... is not trusted\")\n    if input().lower() != \"y\":\n        return None\n```\n \nOn top of that, the SHA256 integrity check is useless here — it validates against a manifest that lives in the same repo the attacker controls, so the hash will always match.\n\n \n## Impact\nAny pipeline using `hub.load()` with `silent=True` and an external repo string is silently loading whatever the repo owner ships. If that model executes arbitrary code on load, the attacker has access to the machine.\n \n## Resolved by removing the feature \n## References\n \n- [Write-up](https://github.com/ZeroXJacks/CVEs/blob/main/2026/CVE-2026-28500.md)",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "onnx"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.21.0rc1"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 1.20.1"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/onnx/onnx/security/advisories/GHSA-hqmj-h5c6-369m"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-28500"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/ZeroXJacks/CVEs/blob/main/2026/CVE-2026-28500.md"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/onnx/onnx"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/pypa/advisory-database/tree/main/vulns/onnx/PYSEC-2026-103.yaml"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-345", "CWE-494", "CWE-693" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-03-16T16:23:28Z",
    "nvd_published_at" : "2026-03-18T02:16:24Z"
  }
}