ipv6: Add lwtunnel encap size of all siblings in nexthop calculation

{
  "id": "a36493ba78e5f9ebc978601ea6297e6ed9f1b159eb314cb42fa329e64c59c08c",
  "url": "https://osv.dev/vulnerability/CVE-2023-53477",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "ipv6: Add lwtunnel encap size of all siblings in nexthop calculation",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: ipv6: Add lwtunnel encap size of all siblings in nexthop calculation In function rt6_nlmsg_size(), the length of nexthop is calculated by multipling the nexthop length of fib6_info and the number of siblings. However if the fib6_info has no lwtunnel but the siblings have lwtunnels, the nexthop length is less than it should be, and it will trigger a warning in inet6_rt_notify() as follows: WARNING: CPU: 0 PID: 6082 at net/ipv6/route.c:6180 inet6_rt_notify+0x120/0x130 ...... Call Trace: fib6_add_rt2node+0x685/0xa30 fib6_add+0x96/0x1b0 ip6_route_add+0x50/0xd0 inet6_rtm_newroute+0x97/0xa0 rtnetlink_rcv_msg+0x156/0x3d0 netlink_rcv_skb+0x5a/0x110 netlink_unicast+0x246/0x350 netlink_sendmsg+0x250/0x4c0 sock_sendmsg+0x66/0x70 ___sys_sendmsg+0x7c/0xd0 __sys_sendmsg+0x5d/0xb0 do_syscall_64+0x3f/0x90 entry_SYSCALL_64_after_hwframe+0x72/0xdc This bug can be reproduced by script: ip -6 addr add 2002::2/64 dev ens2 ip -6 route add 100::/64 via 2002::1 dev ens2 metric 100 for i in 10 20 30 40 50 60 70; do ip link add link ens2 name ipv_$i type ipvlan ip -6 addr add 2002::$i/64 dev ipv_$i ifconfig ipv_$i up done for i in 10 20 30 40 50 60; do ip -6 route append 100::/64 encap ip6 dst 2002::$i via 2002::1 dev ipv_$i metric 100 done ip -6 route append 100::/64 via 2002::1 dev ipv_70 metric 100 This patch fixes it by adding nexthop_len of every siblings using rt6_nh_nlmsg_size().",
    "evidence": "osv:CVE-2023-53477",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "5.4.235",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "5.10.173",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "5.15.100",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.1.18",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.2.5",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2023-53477",
      "aliases": [
        "CVE-2023-53477"
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
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                  "introduced": "beb1afac518dec5a15dc92ba8f0ca016dcf457b4"
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                {
                  "fixed": "aba298b35619213ca787d08d472049627d8cd012"
                },
                {
                  "fixed": "da26369377f0b671c14692e2d65ceb38131053e1"
                },
                {
                  "fixed": "dcdddb5f490890d058ea1f194d661219e92fe88d"
                },
                {
                  "fixed": "e11e4d524eba2d3c8fdf897d7ce3853f7573bae9"
                },
                {
                  "fixed": "aa75d826c221e8d48607aef33836cf872a159cf1"
                },
                {
                  "fixed": "4cc59f386991ec9374cb4bc83dbe1c0b5a95033f"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2023-53477.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "4.11.0"
                },
                {
                  "fixed": "5.4.235"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "5.5.0"
                },
                {
                  "fixed": "5.10.173"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "5.11.0"
                },
                {
                  "fixed": "5.15.100"
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              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "5.16.0"
                },
                {
                  "fixed": "6.1.18"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.2.0"
                },
                {
                  "fixed": "6.2.5"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2023-53477.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:53.491105396Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/4cc59f386991ec9374cb4bc83dbe1c0b5a95033f",
        "https://git.kernel.org/stable/c/aa75d826c221e8d48607aef33836cf872a159cf1",
        "https://git.kernel.org/stable/c/aba298b35619213ca787d08d472049627d8cd012",
        "https://git.kernel.org/stable/c/da26369377f0b671c14692e2d65ceb38131053e1",
        "https://git.kernel.org/stable/c/dcdddb5f490890d058ea1f194d661219e92fe88d",
        "https://git.kernel.org/stable/c/e11e4d524eba2d3c8fdf897d7ce3853f7573bae9",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2023/53xxx/CVE-2023-53477.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2023-53477",
        "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/2023/53xxx/CVE-2023-53477.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2023-53477",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 522002,
  "published_at": "2025-10-01T11:42:46.279+00:00"
}