ONNX: Malicious ONNX models can crash servers by exploiting unprotected object settings.
Summary
The ExternalDataInfo class in ONNX was using Python’s setattr() function to load metadata (like file paths or data lengths) directly from an ONNX model file. The problem? It didn’t check if the "keys" in the file were valid. Because it blindly trusted the file, an attacker could craft a malicious model that overwrites internal object properties.
Why its Dangerous
Instant Crash DoS: An attacker can set the length property to a massive number like 9 petabytes. When the system tries to load the model, it attempts to allocate all that RAM at once, causing the server to crash or freeze Out of Memory.
Access Bypass: By setting a negative offset -1, an attacker can trick the system into reading parts of a file it wasn't supposed to touch.
Object Corruption: Attackers can even inject "dunder" attributes like class to change the object's type entirely, which could lead to more complex exploits.
Fixed: https://github.com/onnx/onnx/pull/7751 object state corruption and DoS via ExternalDataInfo attribute injection
Affected software
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| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Python (PyPI) | onnx | < 1.21.0 | 1.21.0 |
References
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H- Weakness (CWE)
CWE-20, CWE-400, CWE-915- Platform
- Python (PyPI)
- Package
onnx- Disclosed
- 01.04.2026
- Updated
- 11.10.2026 15:17
Sources and licenses
OSV / GitHub Advisory Database - PYSEC-2026-2240 - PyPA Advisory Database; CC BY 4.0
OSV / GitHub Advisory Database - GHSA-538c-55jv-c5g9 - CC BY 4.0
Vulnerability history: onnx
All published vulnerabilities of this package (Python (PyPI)), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 13
- First → latest
- 01.2023 07.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- Critical 1
- High 7
- Medium 4
- Low 1
Disclosures per year
- 2023: 1
- 2024: 3
- 2025: 1
- 2026: 8
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ONNX: Malicious ONNX models can crash servers by exploiting unprotected object settings. this entry
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