Heap OOB in `ResourceScatterUpdate`

Impact

An attacker can trigger a read from outside of bounds of heap allocated data by sending invalid arguments to tf.raw_ops.ResourceScatterUpdate:

import tensorflow as tf

v = tf.Variable([b'vvv'])
tf.raw_ops.ResourceScatterUpdate(
  resource=v.handle,
  indices=[0],
  updates=['1', '2', '3', '4', '5'])

The implementation has an incomplete validation of the relationship between the shapes of indices and updates: instead of checking that the shape of indices is a prefix of the shape of updates (so that broadcasting can happen), code only checks that the number of elements in these two tensors are in a divisibility relationship.

Patches

We have patched the issue in GitHub commit 01cff3f986259d661103412a20745928c727326f.

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.