CVE-2026-19577 (GCVE-0-2026-19577)
Vulnerability from cvelistv5 – Published: 2026-10-11 17:14 – Updated: 2026-10-11 17:14
VLAI
EPSS
VEX
Title
Out-of-bounds read in IPv6 route forwarding when the nexthop neighbor has no link-layer address
Summary
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.
Severity
7.1 (High)
CWE
- CWE-125 - bounds
Assigner
References
2 references
Impacted products
1 product
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| zephyrproject | zephyr |
Affected:
1.8.0 , < 4.5.0
(semver)
|
guessed |
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"value": "net_route_ipv6_packet() in subsys/net/ip/route_ipv6.c resolved the nexthop\u0027s link-layer address with net_nbr_get_lladdr(nbr-\u003eidx) 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 \u0026net_neighbor_lladdr[255] \u2014 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.\n\nThe 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\u0027s 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 \u2014 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 \u2014 and then send a packet addressed to that neighbor.\n\nThe 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\u0027s 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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"providerMetadata": {
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"orgId": "e2e69745-5e70-4e92-8431-deb5529a81ad",
"shortName": "zephyr"
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"references": [
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"name": "Fix commit",
"tags": [
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"url": "https://github.com/zephyrproject-rtos/zephyr/commit/b0b0e8973d1967114adbb9ed1611d448b5a46519"
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{
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"url": "https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-vv76-4m89-95q5"
}
],
"title": "Out-of-bounds read in IPv6 route forwarding when the nexthop neighbor has no link-layer address",
"x_generator": {
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}
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"datePublished": "2026-10-11T17:14:55.032Z",
"dateReserved": "2026-08-11T19:57:38.944Z",
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"value": "net_route_ipv6_packet() in subsys/net/ip/route_ipv6.c resolved the nexthop\u0027s link-layer address with net_nbr_get_lladdr(nbr-\u003eidx) 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 \u0026net_neighbor_lladdr[255] \u2014 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.\n\nThe 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\u0027s 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 \u2014 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 \u2014 and then send a packet addressed to that neighbor.\n\nThe 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\u0027s 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."
}
],
"id": "CVE-2026-19577",
"lastModified": "2026-10-11T18:16:58.433",
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}
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Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
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The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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