AZL-89451

HTML::Entities versions before 3.84 for Perl read freed heap memory in decodeentities.

The XS routine backing HTML::Entities::decodeentities cached a pointer (repl) into the entity-value SV returned by hvfetch on the entity2char hash. When the input SV was identical to a value SV in that hash, and that value contained its own key as an entity reference, a later call to growgap() reallocated the SV's PV buffer and freed the backing allocation that repl still pointed into. The subsequent copy loop read repl_len bytes from the freed allocation.

The read may disclose adjacent heap contents into the destination SV.