{"api_version":"1","generated_at":"2026-10-27T03:18:25+00:00","cve":"CVE-2026-98968","urls":{"html":"https://cve.report/CVE-2026-98968","api":"https://cve.report/api/cve/CVE-2026-98968.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-98968","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-98968"},"summary":{"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":"PUBLISHED","assigner":"Linux","published_at":"2026-10-23 13:17:18","updated_at":"2026-10-24 14:16:49"},"problem_types":[],"metrics":[{"version":"3.1","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","type":"Secondary","score":"8.1","severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H","data":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H","baseScore":8.1,"baseSeverity":"HIGH","attackVector":"NETWORK","attackComplexity":"HIGH","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"}},{"version":"3.1","source":"CNA","type":"DECLARED","score":"8.1","severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H","data":{"baseScore":8.1,"baseSeverity":"HIGH","vectorString":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H","version":"3.1"}}],"references":[{"url":"https://git.kernel.org/stable/c/e7183b7d518ce8b3e1f7284f9881d7a87569df14","name":"https://git.kernel.org/stable/c/e7183b7d518ce8b3e1f7284f9881d7a87569df14","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/e7ea63b4195a150604993044ab574d8240f2a399","name":"https://git.kernel.org/stable/c/e7ea63b4195a150604993044ab574d8240f2a399","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/95114e421196250e3d9662f12df442799477d3c3","name":"https://git.kernel.org/stable/c/95114e421196250e3d9662f12df442799477d3c3","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/afae89de73dd693cfa329580ba0fba63bd3f0a11","name":"https://git.kernel.org/stable/c/afae89de73dd693cfa329580ba0fba63bd3f0a11","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/181cb48c1e9af6b402567e132f879f89d1c54131","name":"https://git.kernel.org/stable/c/181cb48c1e9af6b402567e132f879f89d1c54131","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-98968","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-98968","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected cbc21dc1cfe949e37b2a54c71511579f1899e8d4 95114e421196250e3d9662f12df442799477d3c3 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected cbc21dc1cfe949e37b2a54c71511579f1899e8d4 e7183b7d518ce8b3e1f7284f9881d7a87569df14 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected cbc21dc1cfe949e37b2a54c71511579f1899e8d4 181cb48c1e9af6b402567e132f879f89d1c54131 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected cbc21dc1cfe949e37b2a54c71511579f1899e8d4 e7ea63b4195a150604993044ab574d8240f2a399 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected cbc21dc1cfe949e37b2a54c71511579f1899e8d4 afae89de73dd693cfa329580ba0fba63bd3f0a11 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 5.16","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 5.16 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.6.160 6.6.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.12.113 6.12.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.18.57 6.18.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.2.11 7.2.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.3 * original_commit_for_fix","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":null,"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"defaultStatus":"unaffected","product":"Linux","programFiles":["drivers/net/amt.c","include/net/amt.h"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"lessThan":"95114e421196250e3d9662f12df442799477d3c3","status":"affected","version":"cbc21dc1cfe949e37b2a54c71511579f1899e8d4","versionType":"git"},{"lessThan":"e7183b7d518ce8b3e1f7284f9881d7a87569df14","status":"affected","version":"cbc21dc1cfe949e37b2a54c71511579f1899e8d4","versionType":"git"},{"lessThan":"181cb48c1e9af6b402567e132f879f89d1c54131","status":"affected","version":"cbc21dc1cfe949e37b2a54c71511579f1899e8d4","versionType":"git"},{"lessThan":"e7ea63b4195a150604993044ab574d8240f2a399","status":"affected","version":"cbc21dc1cfe949e37b2a54c71511579f1899e8d4","versionType":"git"},{"lessThan":"afae89de73dd693cfa329580ba0fba63bd3f0a11","status":"affected","version":"cbc21dc1cfe949e37b2a54c71511579f1899e8d4","versionType":"git"}]},{"defaultStatus":"affected","product":"Linux","programFiles":["drivers/net/amt.c","include/net/amt.h"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"status":"affected","version":"5.16"},{"lessThan":"5.16","status":"unaffected","version":"0","versionType":"semver"},{"lessThanOrEqual":"6.6.*","status":"unaffected","version":"6.6.160","versionType":"semver"},{"lessThanOrEqual":"6.12.*","status":"unaffected","version":"6.12.113","versionType":"semver"},{"lessThanOrEqual":"6.18.*","status":"unaffected","version":"6.18.57","versionType":"semver"},{"lessThanOrEqual":"7.2.*","status":"unaffected","version":"7.2.11","versionType":"semver"},{"lessThanOrEqual":"*","status":"unaffected","version":"7.3","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.6.160","versionStartIncluding":"5.16","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.12.113","versionStartIncluding":"5.16","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.18.57","versionStartIncluding":"5.16","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.2.11","versionStartIncluding":"5.16","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.3","versionStartIncluding":"5.16","vulnerable":true}],"negate":false,"operator":"OR"}]}],"descriptions":[{"lang":"en","value":"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)."}],"metrics":[{"cvssV3_1":{"baseScore":8.1,"baseSeverity":"HIGH","vectorString":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H","version":"3.1"},"scenarios":[{"lang":"en","value":"AV:N - A routable UDP AMT_MSG_REQUEST enters udp_rcv() and amt_rcv(), and amt_request_handler() uses its source tuple, nonce, and p bit in the patched amt_send_igmp_gq()/amt_send_mld_gq(); the resulting query later dequeues into patched amt_dev_xmit().\nAC:H - The remote attacker can send the Request and let the tunnel expire, but cannot arrange the required relay-local queue retention: the demonstrated trigger uses igmp_qrv=1 for a 135-second amt_gmi() and a 180-second netem delay. Success therefore depends on target state outside remote control.\nPR:N - The relay branch of amt_rcv() dispatches AMT_MSG_REQUEST directly to amt_request_handler(), which checks only length and reserved/version bits before creating a tunnel; it requires no Discovery state, nonce/MAC validation, credentials, or capability.\nUI:N - Once the relay and delaying qdisc exist, the attacker only sends a Request; amt_request_handler() schedules gc_wq, and amt_tunnel_expire() plus netem dequeue run without victim action.\nS:U - The freed amt_tunnel_list and the accesses from amt_dev_xmit()/amt_send_membership_query() remain within the relay host's kernel; no VM, IOMMU, or other authority boundary is crossed.\nC:H - amt_send_membership_query() reads freed tunnel->ip4, source_port, nonce, and mac, and emits the nonce and MAC in an outbound AMT Membership Query; reclaiming the slab makes this a kernel UAF disclosure primitive.\nI:H - After transmission, amt_update_relay_status() executes spin_lock_bh(&tunnel->lock) and writes tunnel->status through the freed or reallocated amt_tunnel_list, enabling kernel heap corruption and potential control-flow hijacking.\nA:H - The delayed dequeue in amt_dev_xmit() produced the reported KASAN slab-use-after-free; its stale routing, lock, and status accesses can oops, panic, or hang the kernel, and new Requests can trigger it again after tunnel expiry."}]}],"providerMetadata":{"dateUpdated":"2026-10-24T14:09:43.037Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/95114e421196250e3d9662f12df442799477d3c3"},{"url":"https://git.kernel.org/stable/c/e7183b7d518ce8b3e1f7284f9881d7a87569df14"},{"url":"https://git.kernel.org/stable/c/181cb48c1e9af6b402567e132f879f89d1c54131"},{"url":"https://git.kernel.org/stable/c/e7ea63b4195a150604993044ab574d8240f2a399"},{"url":"https://git.kernel.org/stable/c/afae89de73dd693cfa329580ba0fba63bd3f0a11"}],"title":"amt: send the relay's General Query directly from the receive path","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-98968","datePublished":"2026-10-23T12:19:39.236Z","dateReserved":"2026-09-25T10:25:14.383Z","dateUpdated":"2026-10-24T14:09:43.037Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-10-23 13:17:18","lastModifiedDate":"2026-10-24 14:16:49","problem_types":[],"metrics":{"cvssMetricV31":[{"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","type":"Secondary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H","baseScore":8.1,"baseSeverity":"HIGH","attackVector":"NETWORK","attackComplexity":"HIGH","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"},"exploitabilityScore":2.2,"impactScore":5.9}]},"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"98968","Ordinal":"1","Title":"amt: send the relay's General Query directly from the receive pa","CVE":"CVE-2026-98968","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"98968","Ordinal":"1","NoteData":"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).","Type":"Description","Title":"amt: send the relay's General Query directly from the receive pa"}]}}}