{"id":"CVE-2026-19673","url":"https://www.cyber-defence.io/tools/cve/CVE-2026-19673","generatedAt":"2026-10-28T03:32:38.757Z","title":"The result is a reliable remote denial of service and out-of-bounds access with information-disclosure and corruption potential.","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.\n\nA 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().\n\nWith 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.\n\nOnly 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.","published":"2026-10-14T17:18:27.000Z","lastModified":"2026-10-16T16:17:05.000Z","status":"Awaiting Analysis","sourceIdentifier":"vulnerabilities@zephyrproject.org","cvss":{"version":"3.1","score":7.1,"severity":"HIGH","vector":"CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H"},"cwe":["CWE-125"],"affected":[],"epss":{"score":0.00339,"percentile":0.27166,"date":"2026-10-27","history":[{"date":"2026-10-15","score":0.00339,"percentile":0.25694}]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"high","text":"High impact if exploited, but EPSS currently rates exploitation as unlikely (0.34%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit."},"changes":[{"kind":"new","label":"New CVE","at":"2026-10-14T17:18:27.000Z","detail":{"score":"7.1","severity":"HIGH","publishedAt":"2026-10-14T17:18:26.800Z"},"summary":"New CVE, high severity (CVSS 7.1)."}],"references":[{"url":"https://github.com/zephyrproject-rtos/zephyr/commit/fd3c6fedf6b639977a80e52b680b15672c31f3ef","source":"vulnerabilities@zephyrproject.org"},{"url":"https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-79rf-rwff-f4vg","source":"vulnerabilities@zephyrproject.org"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-19673","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}