Cpanel::JSON::XS versions before 4.80 for Perl leak the decoded arguments of a tagged value when its THAW method dies in decode_tag. With allow_tags, a tagged value's class name and argument array are decoded and passed to the class's THAW method. Both are released only after THAW returns, so a THAW that dies leaves the whole decoded argument structure allocated. Each rejected document leaks data of a size the sender chooses, so a process that catches the error and keeps running exhausts its memory.
https://metacpan.org/release/RURBAN/Cpanel-JSON-XS-4.80/changes
https://github.com/rurban/Cpanel-JSON-XS/commit/9ab010221c069a7af9ef7463454ecd3b8ace9c58.patch