CVE-2026-19673
7.1HighPublished 14 Oct 2026 · NVD status: Awaiting Analysis · AI triage by gemini-3.8-flash
- Attack vector
- Adjacent network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
- Impact
- High impact on availability
- Weakness
- CWE-125
Impact
Adjacent unauthenticated attackers can crash the node or leak memory via out-of-bounds reads using a single short Ethernet frame. They only need local network access to send an undersized broadcast packet with a VLAN ethertype.
Root cause
The Ethernet receive path fails to verify that the buffer holds at least 18 bytes before parsing a VLAN header, causing an integer underflow in the buffer length.
Affected systems
Versions not listed — check the vendor advisory.
CVSS v3.1 · CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H
Fix & remediation
Apply Zephyr commit fd3c6fedf6b639977a80e52b680b15672c31f3ef. As an interim workaround, disable CONFIG_NET_VLAN in your build configuration, enable hardware VLAN stripping (ETHERNET_HW_VLAN_TAG_STRIP), or enable CONFIG_NET_BUF_HARDENING.
AI-suggested. Run it in staging first and check it against the vendor advisory. Why?
NVD description
ethernet_recv() in subsys/net/l2/ethernet/ethernet.c validates only that the first net_buf of a received frame holds a plain 14-byte struct net_eth_hdr. When the ethertype is 0x8100 and VLAN is enabled on the interface, the same buffer is reinterpreted as the 18-byte struct net_eth_vlan_hdr without re-checking the length: the VLAN TCI and the inner ethertype are read from offsets 14..17, past pkt->buffer->len, and hdr_len is raised to 18 so the subsequent net_buf_pull() removes more bytes than the buffer holds. A single unauthenticated frame of 14 to 17 bytes carrying the VLAN ethertype triggers this. No knowledge of the node's VLAN configuration is needed: net_eth_get_vlan_iface() returns the base interface for the priority tag 0, and a broadcast destination address satisfies the "frame is for me" test, so a 16-byte broadcast frame with ethertype 0x8100 and TCI 0x0000 reaches the pull. Nothing in the receive path enforces the 60-byte Ethernet minimum — the USB CDC ECM and CDC NCM gadget classes in particular hand host-supplied frames of any non-zero length straight to net_recv_data(). With assertions enabled, net_buf_simple_pull() asserts and the node panics. In a production build (assertions and CONFIG_NET_BUF_HARDENING off) the uint16_t buffer length underflows to 65534 and buf->data is advanced past the end of the fragment's storage, so every later parser reads far outside the buffer and any net_buf_add() on that fragment computes tailroom from the underflowed length. The result is a reliable remote denial of service and out-of-bounds access with information-disclosure and corruption potential. Only configurations built with CONFIG_NET_VLAN=y that have a VLAN enabled on the receiving Ethernet interface, and whose MAC does not strip VLAN tags in hardware (ETHERNET_HW_VLAN_TAG_STRIP), are affected. The fix rejects the frame before the tag is read, so hdr_len is thereafter either 14 or 18 with both sizes validated against pkt->buffer->len.