onnx up to 1.20.x Model setattr input validation

Summaryinfo

A vulnerability was found in onnx up to 1.20.x. It has been rated as critical. Affected by this vulnerability is the function setattr of the component Model Handler. This manipulation causes input validation. The identification of this vulnerability is CVE-2026-34445. It is possible to initiate the attack remotely. There is no exploit available. Upgrading the affected component is advised.

Detailsinfo

A vulnerability has been found in onnx up to 1.20.x and classified as critical. Affected by this vulnerability is the function setattr of the component Model Handler. The manipulation with an unknown input leads to a input validation vulnerability. The CWE definition for the vulnerability is CWE-20. The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

Open Neural Network Exchange (ONNX) is an open standard for machine learning interoperability. Prior to version 1.21.0, 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. It didn’t check if the "keys" in the file were valid. Due to this, an attacker could craft a malicious model that overwrites internal object properties. This issue has been patched in version 1.21.0.

It is possible to read the advisory at github.com. This vulnerability is known as CVE-2026-34445 since 03/27/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. Technical details of the vulnerability are known, but there is no available exploit.

Upgrading to version 1.21.0 eliminates this vulnerability. Applying the patch e30c6935d67cc3eca2fa284e37248e7c0036c46b is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Name

• onnx

Version

• 1.0
• 1.1
• 1.2
• 1.3
• 1.4
• 1.5
• 1.6
• 1.7
• 1.8
• 1.9
• 1.10
• 1.11
• 1.12
• 1.13
• 1.14
• 1.15
• 1.16
• 1.17
• 1.18
• 1.19
• 1.20

License

• open-source

Website

• Product: https://github.com/onnx/onnx/

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