---
id: CVE-2026-18415
title: >-
  ieee802154_send() in subsys/net/l2/ieee802154/ieee802154.c copies the outgoing
  packet into a single fixed 125-byte transmit buffer (tx_frame_buf_pool, sized
  IEEE802154_MTU)
summary: >-
  ieee802154_send() in subsys/net/l2/ieee802154/ieee802154.c copies the outgoing
  packet into a single fixed 125-byte transmit buffer (tx_frame_buf_pool, sized
  IEEE802154_MTU). In builds with CONFIG_NET_L2_IEEE802154_FRAGMENT enabled (the
  d…
severity: medium
cvss: 6.3
cvssVector: 'CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:H'
cwe:
  - CWE-787
vendor: zephyrproject
product: zephyr
affected:
  - zephyr >= 3.2.0 < 4.4.2
published: '2026-09-28'
updated: '2026-09-28'
sourceUpdated: '2026-09-28T21:17:17.403'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-18415'
references:
  - url: >-
      https://github.com/zephyrproject-rtos/zephyr/commit/3d4c6177d2dbd77d12d9b14cd75a00cdbd826227
    label: vulnerabilities@zephyrproject.org
  - url: >-
      https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-j76j-jrjc-xgvp
    label: vulnerabilities@zephyrproject.org
tags:
  - nvd
  - cve.org
ingestedAt: '2026-09-28T21:20:54.786Z'
---

## Overview

ieee802154_send() in subsys/net/l2/ieee802154/ieee802154.c copies the outgoing packet into a single fixed 125-byte transmit buffer (tx_frame_buf_pool, sized IEEE802154_MTU). In builds with CONFIG_NET_L2_IEEE802154_FRAGMENT enabled (the default whenever CONFIG_NET_6LO is set), the branch taken when 6LoWPAN fragmentation is not required performed an unchecked net_buf_add_mem(frame_buf, pkt_buf->data, pkt_buf->len). The only guard was __ASSERT_NO_MSG() inside net_buf_simple_add(), which is compiled out without CONFIG_ASSERT, so an oversized packet silently overran the frame buffer.

The defect is not reachable from the radio: for NET_AF_INET6 packets ieee802154_6lo_encode_pkt() compares the whole packet length against IEEE802154_MTU and takes the fragmentation path when it does not fit, so every buffer copied on the unfragmented branch is within bounds. It is reachable through NET_AF_PACKET sockets bound to an 802.15.4 interface: for NET_SOCK_RAW the 6LoWPAN block is skipped entirely and for NET_SOCK_DGRAM it returns early on the address-family test, leaving no length validation anywhere on the transmit path (net_context_sendto() and net_if_tx() apply none, and pkt_buffer_length() does not clamp the allocation for this L2).

An application — or, in a CONFIG_USERSPACE build, an unprivileged application thread using the zsock_socket()/zsock_sendto() syscalls — can therefore drive a supervisor-mode out-of-bounds write of chosen bytes past the 125-byte pool buffer. With the default CONFIG_NET_BUF_FIXED_DATA_SIZE of 128 bytes the overrun is bounded to roughly ll_hdr_len + 3 bytes; with CONFIG_NET_BUF_VARIABLE_DATA_SIZE a single storage buffer can be as large as CONFIG_NET_PKT_BUF_TX_DATA_POOL_SIZE, making the overrun far larger. The consequence is corruption of memory adjacent to the pool, with a crash or further compromise of kernel state as the practical impact.

The fix validates ll_hdr_len + net_pkt_get_len(pkt) + authtag_len against IEEE802154_MTU before any copy and adds a tailroom-checking copy_pkt_to_frame() helper that returns -EMSGSIZE instead of overrunning the buffer. The same change also linearizes the whole net_buf chain into one MAC frame, so packet storage boundaries no longer become frame boundaries on the wire.

## Remediation

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