{"schema":"threatline.record/2","record":{"id":"CVE-2026-19673","aliases":["GHSA-79rf-rwff-f4vg"],"summary":"Out-of-bounds read and net_buf length underflow in Zephyr Ethernet L2 when parsing a truncated VLAN header","details":"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.","categories":["Unclassified"],"product":"zephyr","vendor":"zephyrproject","ecosystem":null,"affected_ranges":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-19673","source_modified_at":"2026-10-16T15:31:46.383Z","fetched_at":"2026-10-23T18:48:36.087640Z","product":"zephyr","vendor":"zephyrproject","versions":[{"version":"1.12.0","status":"affected","lessThan":"4.5.0","versionType":"semver"}],"defaultStatus":"unaffected"}],"fixed_versions":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-19673","source_modified_at":"2026-10-16T15:31:46.383Z","fetched_at":"2026-10-23T18:48:36.087640Z","package":{"name":"zephyr","ecosystem":null},"version":"4.5.0","basis":"first unaffected version stated in the CVE record"}],"cvss":7.1,"severity":"High","kev":{"listed":false},"epss":{"probability":0.00339,"percentile":0.2612,"score_date":"2026-10-23"},"published_at":"2026-10-14T16:45:57.967Z","modified_at":"2026-10-16T15:31:46.383Z","provenance":[{"source":"CVE List","url":"https://www.cve.org/CVERecord?id=CVE-2026-19673","fetched_at":"2026-10-23T18:48:36.087640Z","source_modified_at":"2026-10-16T15:31:46.383Z"},{"source":"EPSS","url":"https://api.first.org/data/v1/epss?cve=CVE-2026-19673","fetched_at":"2026-10-23T18:42:43.628194Z","source_modified_at":"2026-10-23"}],"sources":["CVE List","EPSS"],"references":[{"source":"CVE List","url":"https://github.com/zephyrproject-rtos/zephyr/commit/fd3c6fedf6b639977a80e52b680b15672c31f3ef","tags":["patch"]},{"source":"CVE List","url":"https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-79rf-rwff-f4vg"}],"locations":[],"motoko_assessment":{"status":"requires_architecture_review","automatic_remediation":false},"cve_state":"PUBLISHED","cvss_source":"CVE List","ssvc":{"exploitation":"none","automatable":"no","technical_impact":"partial","assessed_at":"2026-10-16T15:25:19.143054Z"},"classification":{"method":"product-first software-layer rules","rules_version":"2.1","matched_on":null,"confidence":"unknown","reviewed":false},"change_timestamp":"2026-10-16T15:31:46.383Z","content_hash":"90a643a05ff6a2ad19c50bbaac328a05de61d11f585123d1fb7bb154e5bae272"}}