ipv4: fib: Don't dump dying fib_info in fib_leaf_notify().

{
  "id": "edde306781881c04b98500332929470055ae0bbc9fdd4cc345c070cfbbc5c46c",
  "url": "https://osv.dev/vulnerability/CVE-2026-74289",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "ipv4: fib: Don't dump dying fib_info in fib_leaf_notify().",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: ipv4: fib: Don't dump dying fib_info in fib_leaf_notify(). syzbot reported use-after-free in nsim_fib4_prepare_event(). [0] The problem is that the following functions call fib_info_hold() / refcount_inc() while dumping fib_info under RCU, which is unsafe. * mlxsw_sp_router_fib4_event() * rocker_router_fib_event() * nsim_fib4_prepare_event() refcount_inc_not_zero() must be used, but it would be too late there. Let's guarantee the lifetime of fib_info in fib_leaf_notify(). Note that IPv6 does not need the corresponding change since fib6_table_dump() holds fib6_table.tb6_lock. [0]: refcount_t: addition on 0; use-after-free. WARNING: lib/refcount.c:25 at refcount_warn_saturate+0x9f/0x110 lib/refcount.c:25, CPU#0: kworker/u8:15/3420 Modules linked in: CPU: 0 UID: 0 PID: 3420 Comm: kworker/u8:15 Not tainted syzkaller #0 PREEMPT_{RT,(full)} Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026 Workqueue: netns cleanup_net RIP: 0010:refcount_warn_saturate+0x9f/0x110 lib/refcount.c:25 Code: eb 66 85 db 74 3e 83 fb 01 75 4c e8 1b f1 22 fd 48 8d 3d 84 cb f1 0a 67 48 0f b9 3a eb 4a e8 08 f1 22 fd 48 8d 3d 81 cb f1 0a <67> 48 0f b9 3a eb 37 e8 f5 f0 22 fd 48 8d 3d 7e cb f1 0a 67 48 0f RSP: 0018:ffffc9000f2c7270 EFLAGS: 00010293 RAX: ffffffff84a18858 RBX: 0000000000000002 RCX: ffff888032ff9ec0 RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff8f9353e0 RBP: 0000000000000000 R08: f",
    "evidence": "osv:CVE-2026-74289",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.1.189",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.6.158",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.12.111",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.18.53",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "7.1.5",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-74289",
      "aliases": [
        "CVE-2026-74289"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:L/AC:L/PR:L/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": "c3852ef7f2f8f75a9f85a864bec1f6f5a3068eea"
                },
                {
                  "fixed": "8bdb20b8a581495062b5879f4e9d435da648b3b0"
                },
                {
                  "fixed": "7907a395701b339c2d68f37456d395e953c74795"
                },
                {
                  "fixed": "7980a13add57f97c5da1dc961d0145a6ad2a7f98"
                },
                {
                  "fixed": "bea03e887db5a8a79234531faf14cf2c4d8816c3"
                },
                {
                  "fixed": "676482da8d938ea72c26da0fc86af2d2ec238ab2"
                },
                {
                  "fixed": "06b693d2eb6651a63ad85bad8673de3b7d4edd6d"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-74289.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "4.10.0"
                },
                {
                  "fixed": "6.1.189"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.2.0"
                },
                {
                  "fixed": "6.6.158"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.7.0"
                },
                {
                  "fixed": "6.12.111"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.13.0"
                },
                {
                  "fixed": "6.18.53"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.19.0"
                },
                {
                  "fixed": "7.1.5"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-74289.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:41.422610217Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/06b693d2eb6651a63ad85bad8673de3b7d4edd6d",
        "https://git.kernel.org/stable/c/676482da8d938ea72c26da0fc86af2d2ec238ab2",
        "https://git.kernel.org/stable/c/7907a395701b339c2d68f37456d395e953c74795",
        "https://git.kernel.org/stable/c/7980a13add57f97c5da1dc961d0145a6ad2a7f98",
        "https://git.kernel.org/stable/c/8bdb20b8a581495062b5879f4e9d435da648b3b0",
        "https://git.kernel.org/stable/c/bea03e887db5a8a79234531faf14cf2c4d8816c3",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/74xxx/CVE-2026-74289.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-74289",
        "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/2026/74xxx/CVE-2026-74289.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-74289",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 509185,
  "published_at": "2026-08-15T05:57:56.383+00:00"
}