I wrote something similar but for the ZIP format, called Pure, to detect hidden buffer bleeds outside and between and within structures, amongst other anomalies. It's also amazing what you can do with a ZIP file.

Pure: https://github.com/ronomon/pure

The goal of Pure is to reduce the attack surface available for zero-days by doing the simple yet critical buffer bounds checks that most end-user application software will not, and to do this for more and more popular file formats.

The vision is that one day you can deploy Pure at your email server and get much stronger guarantees on the safety of email attachments that you open... as well as on the attachments you send out... for example that your billing software is not leaking the contents of sensitive server memory into XLSX reports that you are mass mailing to clients (Pure actually found two cases of prominent investment firms that were doing just this).

It's like type checking or linting but for everyday file formats.