PYSEC-2021-842

TensorFlow is an open source platform for machine learning. In affected versions the implementation of tf.math.segment_* operations results in a CHECK-fail related abort (and denial of service) if a segment id in segment_ids is large. This is similar to CVE-2021-29584 (and similar other reported vulnerabilities in TensorFlow, localized to specific APIs): the implementation (both on CPU and GPU) computes the output shape using AddDim. However, if the number of elements in the tensor overflows an int64_t value, AddDim results in a CHECK failure which provokes a std::abort. Instead, code should use AddDimWithStatus. The fix will be included in TensorFlow 2.7.0. We will also cherrypick this commit on TensorFlow 2.6.1, TensorFlow 2.5.2, and TensorFlow 2.4.4, as these are also affected and still in supported range.