{
  "schema_version": "1.6.1",
  "id": "RPI-CVE-2026-68323",
  "modified": "2026-10-09T11:39:44Z",
  "upstream": [
    "CVE-2026-68323"
  ],
  "published": "2026-08-10T12:08:00Z",
  "summary": "tipc: serialize udp bearer replicast list updates",
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\ntipc: serialize udp bearer replicast list updates\n\ntipc_udp_rcast_add() and cleanup_bearer() both update ub->rcast.list with\nlist_add_rcu() / list_del_rcu(), but nothing serializes them. The add runs\nfrom the encap receive softirq (via tipc_udp_rcast_disc()) without\nrtnl_lock(), so it can race the cleanup delete and corrupt the list:\n\n  list_del corruption. prev->next should be ffff8880298d7ab8,\n    but was ffff88802449ad38. (prev=ffff888027e3ec98)\n  kernel BUG at lib/list_debug.c:62!\n  RIP: __list_del_entry_valid_or_report+0x17a/0x200\n  Workqueue: events cleanup_bearer\n  Call Trace:\n   cleanup_bearer (net/tipc/udp_media.c:811)\n   process_one_work (kernel/workqueue.c:3302)\n   worker_thread (kernel/workqueue.c:3466)\n\nThe bearer can be enabled from an unprivileged user namespace, as the\nTIPCv2 generic-netlink ops carry no GENL_ADMIN_PERM.\n\nAdd a spinlock to struct udp_bearer and take it around the list_add_rcu()\nin tipc_udp_rcast_add() and the list_del_rcu() loop in cleanup_bearer() so\nthe two writers can no longer corrupt the list.\n\nReject a duplicate peer under the same lock before allocating, and remove\ntipc_udp_is_known_peer(). The old lockless pre-check in\ntipc_udp_rcast_disc() was racy: two softirqs discovering the same peer\ncould both find it absent and add it twice.\n\ncleanup_bearer() runs from a workqueue after tipc_udp_disable() clears the\nbearer's up bit, so an encap softirq can still reach tipc_udp_rcast_add()\nand add a peer after cleanup_bearer() has already emptied the list, leaking\nthat entry when the bearer is freed. Mark the bearer disabled under\nrcast_lock once the list is emptied and refuse further additions.",
  "severity": [
    {
      "type": "CVSS_V3",
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"
    }
  ],
  "affected": [
    {
      "package": {
        "ecosystem": "Raspberry Pi OS:12",
        "name": "linux"
      },
      "versions": [
        "1:6.1.47-1+rpt4"
      ],
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-2712",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v6",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v7",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v7l",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v8",
            "binary_version": "1:6.1.47-1+rpt4"
          }
        ]
      },
      "database_specific": {
        "per_version": {
          "1:6.1.47-1+rpt4": {
            "linux_commit": "655fc658a15ae7a6f37103754adb39ba52a9a14e",
            "upstream_version": "6.1.47",
            "assessment": "commit ancestry (strak rule)",
            "upstream_fixed": null,
            "compiled_filter": false
          }
        }
      }
    }
  ],
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-68323"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/d70c81001df9320d3445e664428a1d408b5ba896"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/350e592ff4e30e48ffb55e142d11a73e63f4869c"
    }
  ],
  "database_specific": {
    "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git",
    "upstream_modified": "2026-08-17T05:24:08Z",
    "severity": {
      "source": "kernel CNA",
      "cvss_v3_score": 7.8,
      "cvss_v3_severity": "High",
      "scenario": "AV:L - Exploitation requires the local half of the race \u2014 enabling and then disabling a TIPC UDP replicast bearer via generic netlink \u2014 even though the second half is driven by UDP packets; a purely remote peer cannot schedule cleanup_bearer(), so local access is needed.\nAC:L - The attacker owns both racers: they flood LINK_CONFIG UDP packets at the bearer port (softirq list_add_rcu) while issuing TIPC_NL_BEARER_DISABLE (workqueue list_del_rcu), and the window is wide because b->up is cleared before cleanup_bearer is scheduled, so it can be retried until it hits.\nPR:L - TIPC_NL_BEARER_ENABLE/DISABLE/ADD use GENL_UNS_ADMIN_PERM, i.e. CAP_NET_ADMIN in the net's owning user namespace, which any unprivileged user obtains with unshare -Urn; no real root is required.\nUI:N - The attacker performs every step itself \u2014 create netns, enable bearer, send packets, disable bearer \u2014 with no action by any other user or administrator.\nS:U - The corruption and any resulting escalation stay within the kernel's own security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:H - Concurrent list_add_rcu/list_del_rcu on ub->rcast.list leaves dangling and duplicated entries, so udp_replicast objects freed by rcast_free_rcu remain reachable from the list; the resulting use-after-free reads of attacker-groomed heap memory can disclose arbitrary kernel data.\nI:H - List corruption makes list_add_rcu/list_del_rcu write prev->next and next->prev through stale pointers into freed or attacker-controlled heap memory, a classic write primitive that is leverageable for control-flow hijack and privilege escalation.\nA:H - The reported symptom is a hard kernel BUG at lib/list_debug.c:62 (__list_del_entry_valid_or_report) in the cleanup_bearer workqueue, i.e. an immediate panic; without CONFIG_DEBUG_LIST the corrupted list and freed-entry traversal crash the kernel anyway."
    }
  }
}