{"schema":"threatline.record/2","record":{"id":"CVE-2026-98968","aliases":[],"summary":"amt: send the relay's General Query directly from the receive path","details":"In the Linux kernel, the following vulnerability has been resolved:\n\namt: send the relay's General Query directly from the receive path\n\nAn skb queued in a qdisc can outlive the tunnel it references\nthrough a raw pointer in skb->cb. For example, with igmp_qrv set\nto 1 on the relay a tunnel lives for 135s, so a netem delay of\n180s on the amt device outlives it; when the tunnel expires and is\nfreed, the subsequent dequeue triggers a use-after-free in\namt_dev_xmit().\n\n  BUG: KASAN: slab-use-after-free in amt_dev_xmit+0x2763/0x2e20\n  Call Trace:\n   amt_dev_xmit+0x2763/0x2e20 [drivers/net/amt.c:1262]\n   dev_hard_start_xmit+0x22f/0x620\n   sch_direct_xmit+0x12e/0xac0\n   netem_dequeue+0x333/0xc50\n   net_tx_action+0x35c/0xa60\n\namt_send_igmp_gq() and amt_send_mld_gq() are only called from\namt_request_handler(), inside the rcu_read_lock_bh() section of\namt_rcv(). amt_request_handler() already has the tunnel the query is\nfor: it found or created it inside that section. Queuing the query with\ndev_queue_xmit() only leads back into amt_dev_xmit(), which strips the\nEthernet header and calls amt_send_membership_query() for that tunnel.\n\nMake that call directly from the two senders instead, the same way\namt_send_advertisement() transmits from the receive path. The query\nnever waits in a qdisc, the tunnel is only dereferenced inside the\nRCU section that found or created it, and nothing is stored in\nskb->cb, so no lookup or refcount is needed. Remove the query branch\nof amt_dev_xmit(), amt_skb_cb() and struct amt_skb_cb, which have no\nusers left.\n\nBehaviour changes:\n - The relay's own General Queries no longer pass through the amt\n   device's egress path: its qdisc, tc egress (clsact/tcx), the\n   netfilter egress hook and packet taps. They are still visible as\n   UDP on the underlay.\n - A query that is sent successfully is no longer counted as\n   tx_dropped. The old query branch left through the unlock label,\n   which counted every sent query as dropped.\n - A query that reaches amt_dev_xmit() on a relay from elsewhere,\n   such as a userspace querier, is now dropped at the IGMP/MLD type\n   switch. Before, it trusted whatever skb->cb held, and a NULL\n   tunnel hit the WARN_ON(1).","categories":["Operating systems"],"product":"Linux","vendor":"Linux","ecosystem":null,"affected_ranges":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98968","source_modified_at":"2026-10-23T12:19:39.236Z","fetched_at":"2026-10-23T18:42:43.628194Z","product":"Linux","vendor":"Linux","versions":[{"version":"cbc21dc1cfe949e37b2a54c71511579f1899e8d4","lessThan":"95114e421196250e3d9662f12df442799477d3c3","status":"affected","versionType":"git"},{"version":"cbc21dc1cfe949e37b2a54c71511579f1899e8d4","lessThan":"e7183b7d518ce8b3e1f7284f9881d7a87569df14","status":"affected","versionType":"git"},{"version":"cbc21dc1cfe949e37b2a54c71511579f1899e8d4","lessThan":"181cb48c1e9af6b402567e132f879f89d1c54131","status":"affected","versionType":"git"},{"version":"cbc21dc1cfe949e37b2a54c71511579f1899e8d4","lessThan":"e7ea63b4195a150604993044ab574d8240f2a399","status":"affected","versionType":"git"},{"version":"cbc21dc1cfe949e37b2a54c71511579f1899e8d4","lessThan":"afae89de73dd693cfa329580ba0fba63bd3f0a11","status":"affected","versionType":"git"}],"defaultStatus":"unaffected"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98968","source_modified_at":"2026-10-23T12:19:39.236Z","fetched_at":"2026-10-23T18:42:43.628194Z","product":"Linux","vendor":"Linux","versions":[{"version":"5.16","status":"affected"},{"version":"0","lessThan":"5.16","status":"unaffected","versionType":"semver"},{"version":"6.6.160","lessThanOrEqual":"6.6.*","status":"unaffected","versionType":"semver"},{"version":"6.12.113","lessThanOrEqual":"6.12.*","status":"unaffected","versionType":"semver"},{"version":"6.18.57","lessThanOrEqual":"6.18.*","status":"unaffected","versionType":"semver"},{"version":"7.2.11","lessThanOrEqual":"7.2.*","status":"unaffected","versionType":"semver"},{"version":"7.3","lessThanOrEqual":"*","status":"unaffected","versionType":"original_commit_for_fix"}],"defaultStatus":"affected"}],"fixed_versions":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98968","source_modified_at":"2026-10-23T12:19:39.236Z","fetched_at":"2026-10-23T18:42:43.628194Z","package":{"name":"Linux","ecosystem":null},"version":"95114e421196250e3d9662f12df442799477d3c3","basis":"first unaffected version stated in the CVE record"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98968","source_modified_at":"2026-10-23T12:19:39.236Z","fetched_at":"2026-10-23T18:42:43.628194Z","package":{"name":"Linux","ecosystem":null},"version":"181cb48c1e9af6b402567e132f879f89d1c54131","basis":"first unaffected version stated in the CVE record"}],"cvss":null,"severity":null,"kev":{"listed":false},"epss":{"probability":null,"percentile":null,"score_date":null},"published_at":"2026-10-23T12:19:39.236Z","modified_at":"2026-10-23T12:19:39.236Z","provenance":[{"source":"CVE List","url":"https://www.cve.org/CVERecord?id=CVE-2026-98968","fetched_at":"2026-10-23T18:42:43.628194Z","source_modified_at":"2026-10-23T12:19:39.236Z"}],"sources":["CVE List"],"references":[{"source":"CVE List","url":"https://git.kernel.org/stable/c/95114e421196250e3d9662f12df442799477d3c3"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/e7183b7d518ce8b3e1f7284f9881d7a87569df14"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/181cb48c1e9af6b402567e132f879f89d1c54131"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/e7ea63b4195a150604993044ab574d8240f2a399"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/afae89de73dd693cfa329580ba0fba63bd3f0a11"}],"locations":[],"motoko_assessment":{"status":"requires_architecture_review","automatic_remediation":false},"cve_state":"PUBLISHED","classification":{"method":"product-first software-layer rules","rules_version":"2.1","matched_on":"product","confidence":"heuristic","reviewed":false},"change_timestamp":"2026-10-23T12:19:39.236Z","content_hash":"435ec50e75149890afc2f9042c00bb254bf079166307b447fd9c9787c378b777"}}