CVE-2019-16778: In TensorFlow before 1.15, a heap buffer overflow in UnsortedSegmentSum can be produced when the Index template argument

TensorFlow versions before 1.15 had a heap buffer overflow (a type of memory access bug where a program writes beyond the boundaries of allocated memory) in the UnsortedSegmentSum function when using 32-bit integers, causing some large numbers to be incorrectly converted to negative values and leading to out-of-bounds memory access. The vulnerability was considered unlikely to be exploitable and was fixed internally in TensorFlow 1.15 and 2.0.