{
  "schema_version": "1.6.1",
  "id": "RPI-CVE-2026-74609",
  "modified": "2026-10-09T11:39:44Z",
  "upstream": [
    "CVE-2026-74609"
  ],
  "published": "2026-08-22T15:32:12Z",
  "summary": "tipc: read le->link under the node lock in tipc_node_link_down()",
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\ntipc: read le->link under the node lock in tipc_node_link_down()\n\ntipc_node_link_down() caches the link pointer before taking n->lock:\n\n\tstruct tipc_link *l = le->link;\t\t/* unlocked */\n\n\tif (!l)\n\t\treturn;\n\ttipc_node_write_lock(n);\n\tif (!tipc_link_is_establishing(l)) {\t/* deref l */\n\t...\n\t\ttipc_link_reset(l);\t\t/* write into l */\n\tif (delete) {\n\t\tkfree(l);\n\t\tle->link = NULL;\n\nThe delete=true caller frees that very object under n->lock, so the lock\ndoes not protect the cached pointer against it:\n\n - CPU A, delete=false: tipc_rcv() on TIPC_LINK_DOWN_EVT, or the link\n   supervision timer via tipc_node_timeout(), reads l unlocked and then\n   dereferences it under n->lock;\n - CPU B, delete=true: netlink TIPC_NL_BEARER_DISABLE -> bearer_disable()\n   -> tipc_node_delete_links() -> tipc_node_link_down(n, bearer_id, true)\n   -> kfree(l).\n\nThe link is freed with plain kfree(), not kfree_rcu(), and for UDP bearers\ndisable_media() only schedules the asynchronous cleanup_bearer() work, so\nits synchronize_net() runs after the links are already gone.  An in-flight\nCPU A that has read l therefore dereferences freed memory once B frees it:\na use-after-free read in tipc_link_is_establishing(), and a use-after-free\nwrite via tipc_link_reset() on the establishing branch.\n\nThe following trace was captured on 7.2.0-rc5-00284-gaf39eb111ce6:\n\n  BUG: KASAN: slab-use-after-free in tipc_link_is_establishing (net/tipc/link.c:285)\n  Read of size 4 at addr ffff88802e2aa068 by task swapper/2/0\n   tipc_link_is_establishing (net/tipc/link.c:285)\n   tipc_node_link_down (net/tipc/node.c:1076)\n   tipc_node_timeout (net/tipc/node.c:843)\n  Allocated by task 9549:\n   tipc_link_create (net/tipc/link.c:490)\n   tipc_node_check_dest (net/tipc/node.c:1279)\n   tipc_disc_rcv (net/tipc/discover.c:252)\n   tipc_udp_recv (net/tipc/udp_media.c:389)\n  Freed by task 9549:\n   tipc_node_link_down (net/tipc/node.c:1084)\n   tipc_node_delete_links (net/tipc/node.c:1320)\n   bearer_disable (net/tipc/bearer.c:414)\n   __tipc_nl_bearer_disable (net/tipc/bearer.c:992)\n\nMove the le->link read inside tipc_node_write_lock(), so it is serialised\nagainst the kfree() in the delete path.  A racing teardown now either has\nnot run yet, and we see a valid link, or has already run, and we see NULL.",
  "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": "6.1.183",
            "compiled_filter": false
          }
        }
      }
    }
  ],
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-74609"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/2be741ad565c610871a6a95062c12c39da7168fd"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/69d209461c110388710e483a130caf051e4fd09a"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/de017c22135f545ca4e65d1eada22887b64958eb"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/47ba70891b10b2feb52462086b7fcd2ad75d3ce3"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/a714d62513befef37f71f4ae89bb1fe173b65f2e"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/c3f2347a47754eac690967cfd82cb6d559817b07"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/5558a8312452ddb21eff22b1cbd84302ad951944"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/cba9ccb47e9fa4cc77692fb896cc5ab57a667882"
    }
  ],
  "database_specific": {
    "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git",
    "upstream_modified": "2026-08-25T05:42:41Z",
    "severity": {
      "source": "kernel CNA",
      "cvss_v3_score": 7.8,
      "cvss_v3_severity": "High",
      "scenario": "AV:L - The UAF race requires the delete=true path (kfree) via TIPC_NL_BEARER_DISABLE/bearer_disable() or netns teardown, reachable only through local RTNL/genlink with CAP_NET_ADMIN; remote tipc_rcv() packets alone cannot free links and complete the race.\nAC:L - An attacker with CAP_NET_ADMIN controls both CPUs by scripting bearer disable/netns teardown while concurrently driving link-down events via TIPC traffic or link supervision timers; KASAN reproduced this reliably without uncontrollable victim timing.\nPR:L - Bearer disable and link deletion require CAP_NET_ADMIN (GENL_UNS_ADMIN_PERM on TIPC_NL_BEARER_DISABLE); tipc_genl_family is netns-aware, so unprivileged users obtain effective net-admin via user/network namespaces (unshare -Urn).\nUI:N - No victim interaction is required; the attacker scripts bearer teardown and concurrent TIPC link activity from their own processes without needing another user to mount, open files, or perform administrative actions.\nS:U - Slab UAF corrupts host kernel heap memory within the same kernel security authority; impact is kernel crash or local privilege escalation, not a VM, IOMMU, or cross-container sandbox boundary escape.\nC:H - Slab use-after-free read in tipc_link_is_establishing() dereferences freed tipc_link objects (KASAN-confirmed), enabling disclosure of freed kernel memory and supporting further heap exploitation primitives.\nI:H - On the establishing branch tipc_link_reset() performs multiple writes into the freed tipc_link structure, corrupting kernel heap metadata and adjacent objects in ways exploitable for arbitrary write and control-flow hijacking.\nA:H - KASAN-confirmed slab-use-after-free in tipc_node_link_down() causes kernel oops/panic (observed on swapper during tipc_node_timeout), and the race can be retriggered during bearer teardown loops for reliable denial of service."
    }
  }
}