Cpanel::JSON::XS versions from 4.28 before 4.80 for Perl leak the array collecting duplicate key values under dupkeys as arrayref in decode hv.

With dupkeys as arrayref, the values of a duplicate object key are collected into a new array. An extra reference is never released, so the array and every value in it outlive the decoded structure. The array also leaks when decoding fails after a duplicate key.

Repeatedly decoding untrusted JSON with a duplicate key holding a large value exhausts process memory.