A memory corruption issue was addressed with improved validation. This issue is fixed in macOS Catalina 10.15, tvOS 13. Processing a maliciously crafted movie may result in the disclosure of process memory.
CWE-787 - Out-of-Bounds Write
Out-of-bounds write vulnerability is a memory access bug that allows software to write data past the end or before the beginning of the intended buffer. This may result in the corruption of data, a crash, or arbitrary code execution.