{"id":"CVE-2026-98968","revision":"9ea1ef371fa24b8498ef58994b865616","records":[{"revision":"9ea1ef371fa24b8498ef58994b865616","observedAt":"2026-10-24T16:17:04.479+00:00","statement":{"source":"cve-program","id":"CVE-2026-98968","aliases":[],"title":"amt: send the relay's General Query directly from the receive path","description":"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).","state":0,"publishedAt":"2026-10-23T12:19:39.236+00:00","modifiedAt":"2026-10-24T14:09:43.037+00:00","affected":[{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n \"product\": \"Linux\",\n \"vendor\": \"Linux\",\n \"defaultStatus\": \"unaffected\",\n \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n \"programFiles\": [\n \"drivers/net/amt.c\",\n \"include/net/amt.h\"\n ],\n \"versions\": [\n {\n \"version\": \"cbc21dc1cfe949e37b2a54c71511579f1899e8d4\",\n \"lessThan\": \"95114e421196250e3d9662f12df442799477d3c3\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"cbc21dc1cfe949e37b2a54c71511579f1899e8d4\",\n \"lessThan\": \"e7183b7d518ce8b3e1f7284f9881d7a87569df14\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"cbc21dc1cfe949e37b2a54c71511579f1899e8d4\",\n \"lessThan\": \"181cb48c1e9af6b402567e132f879f89d1c54131\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"cbc21dc1cfe949e37b2a54c71511579f1899e8d4\",\n \"lessThan\": \"e7ea63b4195a150604993044ab574d8240f2a399\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"cbc21dc1cfe949e37b2a54c71511579f1899e8d4\",\n \"lessThan\": \"afae89de73dd693cfa329580ba0fba63bd3f0a11\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n }\n ]\n }"},{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n \"product\": \"Linux\",\n \"vendor\": \"Linux\",\n \"defaultStatus\": \"affected\",\n \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n \"programFiles\": [\n \"drivers/net/amt.c\",\n \"include/net/amt.h\"\n ],\n \"versions\": [\n {\n \"version\": \"5.16\",\n \"status\": \"affected\"\n },\n {\n \"version\": \"0\",\n \"lessThan\": \"5.16\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.6.160\",\n \"lessThanOrEqual\": \"6.6.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.12.113\",\n \"lessThanOrEqual\": \"6.12.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.18.57\",\n \"lessThanOrEqual\": \"6.18.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"7.2.11\",\n \"lessThanOrEqual\": \"7.2.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"7.3\",\n \"lessThanOrEqual\": \"*\",\n \"status\": \"unaffected\",\n \"versionType\": \"original_commit_for_fix\"\n }\n ]\n }"}],"metrics":[{"system":"CVSS 3.1","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H","score":8.1,"severity":"HIGH"}],"references":["https://git.kernel.org/stable/c/95114e421196250e3d9662f12df442799477d3c3","https://git.kernel.org/stable/c/e7183b7d518ce8b3e1f7284f9881d7a87569df14","https://git.kernel.org/stable/c/181cb48c1e9af6b402567e132f879f89d1c54131","https://git.kernel.org/stable/c/e7ea63b4195a150604993044ab574d8240f2a399","https://git.kernel.org/stable/c/afae89de73dd693cfa329580ba0fba63bd3f0a11"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-98968","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-98968","identifiers":["CVE-2026-98968"]},"retained":false,"historicalAffected":[]}],"coverage":[]}