tinytag is a Python library for reading audio file metadata. From 2.0.0 until 2.3.0, an M4A file containing a sub-atom with a size of zero inside a ---- atom can cause the metadata parser to stop advancing through the input. The custom-field atom traversal repeatedly processes the malformed location, causing an infinite loop and denying service to a program that reads the crafted file. This issue is fixed in version 2.3.0.