CVE-2026-16118: Xdgmime: heap-based buffer overflow in _xdg_mime_magic_parse_magic_line() in xdgmimemagic.c

A flaw was found in xdgmime, affecting all versions. A heap-based buffer overflow can occur in xdgmimemagicparsemagicline() in the xdgmimemagic.c file on little-endian systems when an attacker-controlled MIME magic file in a user-writable XDG data location (e.g., in the $XDGDATAHOME/mime/magic path) is parsed by an application performing MIME type detection (e.g., via gcontenttypeguess()). When performing byte-swap, incorrect pointer arithmetic on the write side causes an out-of-bounds write of 2 bytes, resulting in an application crash or memory corruption. To exploit this flaw, an attacker must trick a user into installing a malicious MIME magic file.