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19Track

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

onnx · CVE-2026-115922
0 news outlets1 CERTs and agencies0 research labs

Assessment: Track

SSVC decision points: exploitation none, automatable no, technical impact partial, deployment low.

What is it?

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.

Evidence

Official warnings1National CERTs, government cyber security agencies and the vendor’s own advisories

Exploitation

  • Exploit code published (not verified by us)
  • Exploited in the wild (confirmed by a source)
  • Listed as known exploited (CISA KEV)
CVSS
6.2
EPSS
0.1%
First seen
13 h ago
Status
confirmed

All onnx vulnerabilities