CVE-2021-37681: Null pointer exception in TensorFlow Lite

Impact The implementation of SVDF in TFLite is vulnerable to a null pointer error:

cc TfLiteTensor state = GetVariableInput(context, node, kStateTensor); // ... GetTensorData<float>(state)

The GetVariableInput function can return a null pointer but GetTensorData assumes that the argument is always a valid tensor.

cc TfLiteTensor GetVariableInput(TfLiteContext context, const TfLiteNode node, int index) { TfLiteTensor tensor = GetMutableInput(context, node, index); return tensor->isvariable ? tensor : nullptr; }

Furthermore, because GetVariableInput calls GetMutableInput which might return nullptr, the tensor->isvariable expression can also trigger a null pointer exception.

Patches We have patched the issue in GitHub commit 5b048e87e4e55990dae6b547add4dae59f4e1c76.

The fix will be included in TensorFlow 2.6.0. We will also cherrypick this commit on TensorFlow 2.5.1, TensorFlow 2.4.3, and TensorFlow 2.3.4, as these are also affected and still in supported range.

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Attribution This vulnerability has been reported by members of the Aivul Team from Qihoo 360.