Description
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.
Published: 2026-09-28
Score: 6.3 Medium
EPSS: < 1% Very Low
KEV: No
Impact: Out-of-bounds write leading to memory corruption that could crash or compromise kernel state
Action: Patch Now
AI Analysis

Impact

The bug resides in ieee802154_send(), which copies an outgoing packet into a fixed 125‑byte transmit buffer without validating the packet length when 6LoWPAN fragmentation is not required. A superuser context write can overflow the buffer by up to several bytes, corrupting adjacent memory and potentially causing a crash or privilege elevation through kernel state compromise.

Affected Systems

Zephyr Project’s Zephyr RTOS network stack for IEEE 802.15.4 L2. The flaw appears in builds where CONFIG_NET_L2_IEEE802154_FRAGMENT is enabled (the default when CONFIG_NET_6LO is set). No specific OTA release is cited, but any firmware using the vulnerable Zephyr network stack and allowing applications to create NET_AF_PACKET sockets bound to an 802.15.4 interface is affected.

Risk and Exploitability

The CVSS score is 6.3, indicating a moderate severity. EPSS data is unavailable and the vulnerability is not in the CISA KEV catalog. Attacks must originate from an application or unprivileged thread that can use the zsock_socket()/zsock_sendto() syscalls on NET_AF_PACKET sockets; the radio interface itself does not expose the flaw. Although the attack surface is narrower than a remote network‑side vulnerability, systems that run user‑generated code with raw 802.15.4 transmission capabilities face a non‑negligible risk of success, especially if kernel assertions are disabled.

Generated by OpenCVE AI on September 28, 2026 at 21:39 UTC.

Remediation

No solution or workaround provided in the CVE record.

OpenCVE Recommended Actions

  • Upgrade Zephyr to a version including commit 3d4c6177d2dbd77d12d9b14cd75a00cdbd826227, which adds pre‑copy length validation and a safe copy helper.
  • If an upgrade is not feasible, disable CONFIG_NET_L2_IEEE802154_FRAGMENT or CONFIG_NET_6LO to prevent the unvalidated branch from executing, or enable CONFIG_ASSERT so that the __ASSERT_NO_MSG guard triggers during development.
  • Restrict NET_AF_PACKET socket usage so that only trusted, privileged code can perform raw 802.15.4 transmissions; validate packet lengths locally before sending to avoid overflowing the transmit buffer.

Generated by OpenCVE AI on September 28, 2026 at 21:39 UTC.

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History

Wed, 30 Sep 2026 17:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Mon, 28 Sep 2026 22:00:00 +0000

Type Values Removed Values Added
First Time appeared Zephyrproject
Zephyrproject zephyr
Vendors & Products Zephyrproject
Zephyrproject zephyr

Mon, 28 Sep 2026 20:30:00 +0000

Type Values Removed Values Added
Description 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.
Title Out-of-bounds write in the IEEE 802.15.4 L2 transmit path for oversized non-6LoWPAN frames
Weaknesses CWE-787
References
Metrics cvssV3_1

{'score': 6.3, 'vector': 'CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:H'}

Subscriptions

Zephyrproject Zephyr
cve-icon MITRE

Status: PUBLISHED

Assigner: zephyr

Published:

Updated: 2026-09-30T15:28:20.759Z

Reserved: 2026-07-30T17:54:11.604Z

Link: CVE-2026-18415

cve-icon Vulnrichment

Updated: 2026-09-30T15:27:32.527Z

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-09-28T21:17:17.403

Modified: 2026-09-30T16:17:12.120

Link: CVE-2026-18415

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-09-28T21:45:06Z

Weaknesses