[File] [SECURITY] Integer Overflow in .mgc File nmagic Validation Leading to SIGSEGV (file-5.17)

[Kerwin]

Hi maintainers,

I am reporting an integer overflow vulnerability in libmagic (file-5.17)
where a crafted `.mgc` file exploits a `uint32_t` wraparound in the
`nmagic` sum validation in `apprentice_map()` (apprentice.c:2716-2733),
causing an out-of-bounds pointer and a SIGSEGV crash on the next access.

Please find the detailed vulnerability report and proof-of-concept files
attached.

Best regards
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