CVE-2026-102714

In Eclipse ThreadX NetX Duo versions up to and including 6.5.2.202603, built with IPv6, the ICMPv6 option validator accepts an option area that ends in a one- or two-byte residue, and the Router Advertisement, Neighbor Solicitation, Neighbor Advertisement and Redirect handlers then walk it without length checks. A host on the local link can send one such message to make the IP thread read past the packet or loop forever, and can place off-packet memory in the neighbor cache.

In Eclipse ThreadX NetX Duo versions up to and including 6.5.2.202603, built with IPv6, the ICMPv6 option validator accepts an option area that ends in a one- or two-byte residue, and the Router Advertisement, Neighbor Solicitation, Neighbor Advertisement and Redirect handlers then walk it without length checks. A host on the local link can send one such message to make the IP thread read past the packet or loop forever, and can place off-packet memory in the neighbor cache.

_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.

In Eclipse ThreadX NetX Duo versions up to and including 6.5.2.202603, built with IPv6, the ICMPv6 option validator accepts an option area that ends in a one- or two-byte residue, and the Router Advertisement, Neighbor Solicitation, Neighbor Advertisement and Redirect handlers then walk it without length checks. A host on the local link can send one such message to make the IP thread read past the packet or loop forever, and can place off-packet memory in the neighbor cache.

In Eclipse ThreadX NetX Duo versions up to and including 6.5.2.202603, built with IPv6, the ICMPv6 option validator accepts an option area that ends in a one- or two-byte residue, and the Router Advertisement, Neighbor Solicitation, Neighbor Advertisement and Redirect handlers then walk it without length checks. A host on the local link can send one such message to make the IP thread read past the packet or loop forever, and can place off-packet memory in the neighbor cache.