GHSA-6pwm-x34p-fvj2 ONNX: Out-of-bounds read in ConvTranspose shape inference via undersized weight rank

• PyPI onnx: >= 1.2.1, < 1.22.0 → fixed in 1.22.0

Summary ONNX ConvTranspose shape inference performed an out-of-bounds read when the weight tensor had fewer than three dimensions and the model did not provide a `kernel_shape` attribute. The inference function derived an empty `effective_kernel_shape` vector from the undersized weight tensor, then indexed that vector once for each spatial dimension of the input tensor. A crafted model passed `onnx.checker.check_model()` and caused SIGSEGV when passed to `onnx.shape_inference.infer_shapes()`. Technical details For an input shape such as `[1, 1, 5]`, shape inference computes one spatial input dimension. A weight shape such as `[1, 3]` has no spatial dimensions, so deriving `kernel_shape` from dimensions 2 onward produces an empty vector. The output loop nevertheless accesses `effective_kernel_shape[0]`. The defect affected both the older `convTransposeShapeInference_opset11()` path and the then-current ConvTranspose inference implementation. Impact An application that performs shape inference on an untrusted model can be terminated, causing denial of service. The observed result was a deterministic process crash. No confidentiality or integrity impact was demonstrated. Affected versions • Affected: ONNX 1.2.1 through 1.21.0 • Patched: ONNX 1.22.0 Remediation Upgrade to ONNX 1.22.0 or later. The fix rejects input and weight tensors with fewer than three dimensions before deriving the spatial kernel shape. • Fix: onnx/onnx#7997 • Commit: `2ec288908` The original malformed model was re-tested against the published ONNX 1.23.2 wheel and correctly raises `InferenceError`. Severity The vulnerable ONNX component processes the malicious model through a local library API or file boundary and is not itself bound to a network stack. Applications that expose ONNX model processing over a network should calculate an Environmental score with Modified Attack Vector set to Network.