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CVE-2026-19577
net_route_ipv6_packet() in subsys/net/ip/route_ipv6.c resolved the nexthop's link-layer address with net_nbr_get_lladdr(nbr->idx) without first checking whether the neighbor cache entry actually had a linked link-layer address. An unresolved neighbor carries idx == NET_NBR_LLADDR_UNKNOWN (0xff), and net_nbr_get_lladdr() in subsys/net/ip/nbr.c performs no runtime bounds check beyond a NET_ASSERT, returning &net_neighbor_lladdr[255] — roughly 2.5 KB past the end of an array whose default size is CONFIG_NET_IPV6_MAX_NEIGHBORS (8). Because the returned pointer is never NULL, the following lladdr == NULL guard does not catch it.
The function is reached from ipv6_route_packet() in subsys/net/ip/ipv6.c for every received unicast IPv6 packet whose destination is not a local address on the receiving interface; CONFIG_NET_IPV6_ROUTE is enabled by default whenever the IPv6 neighbor cache is, so no router or forwarding configuration is needed. net_route_ipv6_get_info() returns the packet's destination itself as the nexthop when a neighbor cache entry for it exists, and the cache lookup does not skip INCOMPLETE entries. An unauthenticated attacker on the same link can therefore force the unresolved state — for example by eliciting traffic to a spoofed, non-existent neighbor address so that net_ipv6_send_ns() creates an INCOMPLETE entry, or by sending a Router Advertisement with no source link-layer address option, which creates a persistently unresolved router neighbor — and then send a packet addressed to that neighbor.
The result is an out-of-bounds read at a fixed index past the neighbor link-layer address array. On builds with CONFIG_ASSERT enabled the assertion fires and the device panics, giving a repeatable remote denial of service. With assertions disabled, the stale out-of-bounds struct net_linkaddr drives a memcmp() over an attacker-uninfluenced length and, when its len byte passes the NET_LINK_ADDR_MAX_LENGTH check, up to 8 bytes of unrelated static RAM are copied into the outgoing frame's destination link-layer address and transmitted on the link, disclosing them to any listener. There is no out-of-bounds write and the offset is not attacker-controlled, which bounds the impact.
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The vulnerability can be exploited over a local network, such as Wi-Fi. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a low impact on the confidentiality of the information. There is a high impact on the availability of the system.
Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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