ipv6: mcast: use rcu_assign_pointer() for __rcu list updates

{
  "id": "494da59c2295cc27513f86ecac622a3b93f2b34a5af02865474ed7a0bba9af25",
  "url": "https://osv.dev/vulnerability/CVE-2026-98099",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "ipv6: mcast: use rcu_assign_pointer() for __rcu list updates",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: ipv6: mcast: use rcu_assign_pointer() for __rcu list updates Several places in net/ipv6/mcast.c update RCU-protected lists (np->ipv6_mc_list, idev->mc_list, idev->mc_tomb) using direct pointer assignments instead of rcu_assign_pointer(): 1. In __ipv6_dev_mc_dec(), unlinking a group from idev->mc_list did: *map = ma->next; without rcu_assign_pointer() while concurrent readers traverse idev->mc_list locklessly under rcu_read_lock(). 2. In ipv6_sock_mc_drop() and __ipv6_sock_mc_close(), unlinking a group from np->ipv6_mc_list directly assigned *lnk = mc_lst->next and np->ipv6_mc_list = mc_lst->next without rcu_assign_pointer(), racing with lockless readers in inet6_mc_check(). 3. In __ipv6_sock_mc_join(), mc_lst->next was initialized to np->ipv6_mc_list via raw assignment before publishing mc_lst. 4. In mld_del_delrec() and __ipv6_dev_mc_inc(), __rcu source pointers passed into rcu_assign_pointer() lacked explicit dereference helpers. Fix these by consistently using rcu_assign_pointer() along with mc_dereference() / sock_dereference().",
    "evidence": "osv:CVE-2026-98099",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.6.160",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.12.114",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.18.57",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "7.2.7",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2026-98099",
      "aliases": [
        "CVE-2026-98099"
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
                {
                  "introduced": "456b61bca8ee324ab6c18b065e632c9a8c88aa39"
                },
                {
                  "fixed": "0e3e3cec28c4d1bf29948da40b4e9e5d44f7852b"
                },
                {
                  "fixed": "49d7e1b456ba2f3ee08b3e264d999c09992cde8e"
                },
                {
                  "fixed": "afca229b39acc2590976b3e4f6e0fe76cededc60"
                },
                {
                  "fixed": "2e46b0c9fcf7e10b64ce1630b925f47918d1f7f6"
                },
                {
                  "fixed": "0c8f56c583c3250408367880c98e4d6fbc929315"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-98099.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "2.6.38"
                },
                {
                  "fixed": "6.6.160"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.7.0"
                },
                {
                  "fixed": "6.12.114"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.13.0"
                },
                {
                  "fixed": "6.18.57"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.19.0"
                },
                {
                  "fixed": "7.2.7"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-98099.json"
          }
        }
      ],
      "modified": "2026-10-30T02:31:06.672676981Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/0c8f56c583c3250408367880c98e4d6fbc929315",
        "https://git.kernel.org/stable/c/0e3e3cec28c4d1bf29948da40b4e9e5d44f7852b",
        "https://git.kernel.org/stable/c/2e46b0c9fcf7e10b64ce1630b925f47918d1f7f6",
        "https://git.kernel.org/stable/c/49d7e1b456ba2f3ee08b3e264d999c09992cde8e",
        "https://git.kernel.org/stable/c/afca229b39acc2590976b3e4f6e0fe76cededc60",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98099.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-98099",
        "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-2026-98099.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-98099",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 491696,
  "published_at": "2026-09-25T10:24:28.929+00:00"
}