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[ CVE-2026-115922 · Published 26 Oct 2026 ]

ONNX: Denial of service via unchecked expansion of packed sub-byte tensors in ONNX Python APIs

CVSS 6.2 EPSS <1%Fix available

[ Description ]Official description

Open Neural Network Exchange (ONNX) is an open standard for machine learning interoperability. Prior to 1.22.0, _unpack_2bit() and _unpack_4bit() resize unpacked arrays according to attacker-controlled TensorProto.dims without verifying that raw_data or int32_data encodes the declared number of elements. Materializing an untrusted UINT2, INT2, UINT4, INT4, or FLOAT4E2M1 tensor through onnx.numpy_helper.to_array() or onnx.reference.ReferenceEvaluator can therefore expand a small packed payload into a disproportionately large allocation and exhaust memory. This issue is fixed in version 1.22.0.

[ Fixes ]Fixes and patches

  • onnx 1.22.0Fixed version · GitHub Advisories · pip package onnx: upgrade to 1.22.0 or later (affected <= 1.21.0)

[ Packages ]Affected open-source packages

[ References ]References