the real fix, which went out in BIND 4.9.5 or perhaps 4.9.4-P1, looks like:

                        if (bp + n >= &hostbuf[sizeof hostbuf]) {
                                dprintf("size (%d) too big\n", n);
                                had_error++;
                                continue;
                        }
+                       if (hap >= &h_addr_ptrs[MAXADDRS-1]) {
+                               if (!toobig++)
+                                       dprintf("Too many addresses (%d)\n",
+                                               MAXADDRS);
+                               cp += n;
+                               continue;
+                       }
                        bcopy(cp, *hap++ = bp, n);
                        bp += n;
                        buflen -= n;
                        cp += n;
                        break;

i am negotiating with the core team to get direct netbsd cvs access so that
i will be able to keep netbsd's BIND server, resolver, and utilities up to
date.  apparently this is hinging on whether netbsd uses IRS or not.