url_host_set() is free-ing and allocating memory at every call which is triggering a crash in the heap code

url_host_set() is calling this function every time:

const char *
mime_str_u16_set (HdrHeap *heap,
const char *s_str,
inku16 s_len,
const char **d_str,
inku16 *d_len,
bool must_copy)
{
// INKqa08287 - keep track of free string space.
// INVARIENT: passed in result pointers must be to
// either NULL or be valid ptr for a string already
// the string heaps
heap->free_string(*d_str, *d_len);

if (must_copy && s_str)

{ s_str = heap->duplicate_str(s_str, s_len); }

*d_str = s_str;
*d_len = s_len;
return(s_str);
}

So it always free()s and allocates a new chunk of memory. The regex mapping code calls url_host_set() on the same URL object every time it finds a mapping. At a high concurrency level, this was triggering a crash in the heap code.