amt: send the relay's General Query directly from the receive path

{
  "id": "fa206874db2b5f4e267a04335bbef26dd44c7e09d2ac2196219dc118abac964c",
  "url": "https://osv.dev/vulnerability/CVE-2026-98968",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "amt: send the relay's General Query directly from the receive path",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: amt: send the relay's General Query directly from the receive path An skb queued in a qdisc can outlive the tunnel it references through a raw pointer in skb->cb. For example, with igmp_qrv set to 1 on the relay a tunnel lives for 135s, so a netem delay of 180s on the amt device outlives it; when the tunnel expires and is freed, the subsequent dequeue triggers a use-after-free in amt_dev_xmit(). BUG: KASAN: slab-use-after-free in amt_dev_xmit+0x2763/0x2e20 Call Trace: amt_dev_xmit+0x2763/0x2e20 [drivers/net/amt.c:1262] dev_hard_start_xmit+0x22f/0x620 sch_direct_xmit+0x12e/0xac0 netem_dequeue+0x333/0xc50 net_tx_action+0x35c/0xa60 amt_send_igmp_gq() and amt_send_mld_gq() are only called from amt_request_handler(), inside the rcu_read_lock_bh() section of amt_rcv(). amt_request_handler() already has the tunnel the query is for: it found or created it inside that section. Queuing the query with dev_queue_xmit() only leads back into amt_dev_xmit(), which strips the Ethernet header and calls amt_send_membership_query() for that tunnel. Make that call directly from the two senders instead, the same way amt_send_advertisement() transmits from the receive path. The query never waits in a qdisc, the tunnel is only dereferenced inside the RCU section that found or created it, and nothing is stored in skb->cb, so no lookup or refcount is needed. Remove the query branch of amt_dev_xmit(), amt_skb_cb() and struct amt_skb_c",
    "evidence": "osv:CVE-2026-98968",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.1.191",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.6.160",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.12.113",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.18.57",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "7.2.11",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-98968",
      "aliases": [
        "CVE-2026-98968"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
                {
                  "introduced": "cbc21dc1cfe949e37b2a54c71511579f1899e8d4"
                },
                {
                  "fixed": "423a46053788ec4a021d57e69d66db7f7f550da4"
                },
                {
                  "fixed": "95114e421196250e3d9662f12df442799477d3c3"
                },
                {
                  "fixed": "e7183b7d518ce8b3e1f7284f9881d7a87569df14"
                },
                {
                  "fixed": "181cb48c1e9af6b402567e132f879f89d1c54131"
                },
                {
                  "fixed": "e7ea63b4195a150604993044ab574d8240f2a399"
                },
                {
                  "fixed": "afae89de73dd693cfa329580ba0fba63bd3f0a11"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-98968.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "5.16.0"
                },
                {
                  "fixed": "6.1.191"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.2.0"
                },
                {
                  "fixed": "6.6.160"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.7.0"
                },
                {
                  "fixed": "6.12.113"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.13.0"
                },
                {
                  "fixed": "6.18.57"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.19.0"
                },
                {
                  "fixed": "7.2.11"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-98968.json"
          }
        }
      ],
      "modified": "2026-11-01T02:30:43.943159707Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/181cb48c1e9af6b402567e132f879f89d1c54131",
        "https://git.kernel.org/stable/c/423a46053788ec4a021d57e69d66db7f7f550da4",
        "https://git.kernel.org/stable/c/95114e421196250e3d9662f12df442799477d3c3",
        "https://git.kernel.org/stable/c/afae89de73dd693cfa329580ba0fba63bd3f0a11",
        "https://git.kernel.org/stable/c/e7183b7d518ce8b3e1f7284f9881d7a87569df14",
        "https://git.kernel.org/stable/c/e7ea63b4195a150604993044ab574d8240f2a399",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98968.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-98968",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98968.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-98968",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 495463,
  "published_at": "2026-10-23T12:19:39.236+00:00"
}