---
id: CVE-2026-10640
title: >-
  Use-after-free reading `net_pkt` `iface` after send in IPv6 Neighbor Discovery
  (`ipv6_nbr.c`)
summary: >-
  Zephyr's IPv6 Neighbor Discovery send paths (net_ipv6_send_na,
  net_ipv6_send_ns, net_ipv6_send_rs in subsys/net/ip/ipv6_nbr.c) updated the
  per-interface ICMP-sent statistics by calling net_pkt_iface(pkt) after
  net_send_data(pkt) had alre…
severity: medium
cvss: 4.2
cvssVector: 'CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:L'
cvssSource: cna
cwe:
  - CWE-416
vendor: zephyrproject
product: zephyr
affected:
  - zephyr >= 3.3.0 < 4.3.1
  - zephyr >= 4.4.0 < 4.4.1
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-06-16T15:28:30.797017Z'
published: '2026-06-16'
updated: '2026-10-15'
sourceUpdated: '2026-10-15T22:10:02.544Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-10640'
references:
  - url: >-
      https://github.com/zephyrproject-rtos/zephyr/commit/aaed8332a62b0490a2f3c2cbabe272f575068eaa
    label: Fix commit
  - url: >-
      https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-r74c-mr4m-7g9g
    label: GHSA-r74c-mr4m-7g9g
tags:
  - cve.org
epss: 0.0037
epssPercentile: 0.29271
ingestedAt: '2026-10-15T22:48:25.563Z'
---

## Overview

Zephyr's IPv6 Neighbor Discovery send paths (net_ipv6_send_na, net_ipv6_send_ns, net_ipv6_send_rs in subsys/net/ip/ipv6_nbr.c) updated the per-interface ICMP-sent statistics by calling net_pkt_iface(pkt) after net_send_data(pkt) had already returned successfully. On the success path the network stack owns and releases the packet's reference (the L2/driver send unrefs it, e.g. ethernet_send -> net_pkt_unref), so for a freshly allocated packet with refcount 1 the net_pkt slab block can be freed before the statistics line runs (synchronously when no TX queue thread is configured, or via a concurrent TX thread otherwise).

The subsequent net_pkt_iface(pkt) reads pkt->iface from the freed slab block, and with CONFIG_NET_STATISTICS_PER_INTERFACE enabled that loaded pointer is dereferenced to increment iface->stats.icmp.sent, a use-after-free (CWE-416). If the slab block was reallocated in the meantime the read/increment targets unrelated or attacker-influenced memory, yielding corrupted statistics, a fault/crash (denial of service), or potential limited memory corruption.

The vulnerable Neighbor Advertisement path is reachable by any unauthenticated on-link node simply by sending ICMPv6 Neighbor Solicitations to a Zephyr node with native IPv6 enabled (handle_ns_input -> net_ipv6_send_na).

Affected from v3.3.0 through v4.4.0; the fix uses the already-available iface argument instead of touching the sent packet. Configurations without per-interface statistics dereference only a global counter and are not affected by the memory-safety aspect.

## Affected

- `zephyr >= 3.3.0 < 4.3.1`
- `zephyr >= 4.4.0 < 4.4.1`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.