Target admission accepted a thin Mach-O after reading only its magic and
CPU type, so a 12-byte prefix opened as a valid arm64 executable and the
first provider query failed as a generic execution failure. ELF headers
were likewise accepted after 20 bytes, and a FAT file whose selected slice
lies beyond its end was admitted.
Require the complete fixed header (Mach-O 28 or 32 bytes, ELF 52 or 64),
Mach-O load commands that fit in the file, and a selected FAT slice within
the file, checking commitments against the file size rather than the
probed prefix. Each refusal names the failed constraint.
Fixes#1189
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>