"_nx_icmpv6_validate_options()" scans the option area with "while (length > 2)" ("common/src/nx_icmpv6_validate_options.c:79"). An area whose size leaves a one- or two-byte residue exits the loop with that tail unexamined; the residue is not negative, so the function returns "NX_SUCCESS". Its zero-length rejection never sees those bytes. Every consumer then re-walks the same area, reading a two-byte option header at the residue and subtracting "nx_icmpv6_option_length << 3" with no zero check and no remaining-length check. Three outcomes follow, selected by bytes the attacker controls. Zero length byte. The walker subtracts zero and advances zero. All four handlers loop forever — "_nx_icmpv6_process_ra" ("nx_icmpv6_process_ra.c:245, :528"), "_nx_icmpv6_process_ns" (":251, :329"), "_nx_icmpv6_process_na" (":147, :156") and "_nx_icmpv6_process_redirect" (":247, :350"). The walk runs in the IP thread, which is the highest-priority thread and does not yield inside the loop, so the system stops until a watchdog reset and the frame can be replayed after each one. Non-zero length byte on a short residue. The three unsigned counters underflow — "2 - 8" becomes "0xFFFFFFFA" — and the walk continues past the packet buffer, reading until it faults or meets a zero length byte and freezes. The Router Advertisement counter is signed and exits cleanly in this case. One-byte residue. The walker reads a two-byte option header, over-reading one byte. During a runaway walk, stray bytes parsing as a link-layer address option are copied into the neighbor cache ("nx_icmpv6_process_ns.c:280, :293") and subsequently used as the destination MAC for frames to that neighbour, placing off-packet memory on the link. Confirmed by inspection, not reproduced.