ipv4: icmp: reject RTN_UNREACHABLE input routes in icmp_route_lookup

{
  "id": "8c1fb908e8f164b79dfc7057b55ef194f692ad299961946b64f6d6cabf73290f",
  "url": "https://osv.dev/vulnerability/CVE-2026-98303",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "ipv4: icmp: reject RTN_UNREACHABLE input routes in icmp_route_lookup",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: ipv4: icmp: reject RTN_UNREACHABLE input routes in icmp_route_lookup When the forward output route cannot be used in icmp_route_lookup(), it enters the \"reverse path\" and calls ip_route_input() on fl4_dec.daddr, the original packet's source address. ip_route_input() only returns an error for truly invalid packets. For unreachable addresses it will succeed and return an input route whose dst.output is set to ip_rt_bug(). The existing check only rejects RTN_LOCAL routes, so the RTN_UNREACHABLE route types can still be returned and later used for output, syzkaller triggering a WARN_ON_ONCE() in ip_rt_bug() as bellow: ------------[ cut here ]------------ WARNING: net/ipv4/route.c:1273 at ip_rt_bug+0x14/0x20 RIP: 0010:ip_rt_bug+0x14/0x20 Call Trace: ip_push_pending_frames+0xfa/0x100 __icmp_send+0x905/0xf10 ip_options_compile+0xc0/0xd0 ip_rcv_finish_core+0x321/0xae0 ip_rcv+0x1de/0x260 __netif_receive_skb_one_core+0x11a/0x130 netif_receive_skb+0x7b/0x260 tun_get_user+0x11bf/0x1c10 ------------[ cut here ]------------ Reject input route that is RTN_UNREACHABLE to fix it. The net warning is only printed for RTN_LOCAL, as RTN_UNREACHABLE is not the result of a race condition.",
    "evidence": "osv:CVE-2026-98303",
    "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": "6.12.112",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.18.54",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "7.2.8",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2026-98303",
      "aliases": [
        "CVE-2026-98303"
      ],
      "affected": [
        {
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              "type": "GIT",
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                  "fixed": "06083cea4a3b95f5ebc85312f97d7086e6c9e782"
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                {
                  "fixed": "83aa83f81a8fec30ff5372dee60b2f0561bcb2ca"
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                {
                  "fixed": "cac69c50716c712ef0114837c9427da66066124c"
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                {
                  "fixed": "1af2d87964d87ba7626d96928d68c09158b5a223"
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                {
                  "fixed": "fda3000147dc96c75ba162f680bec0a9fecf3037"
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                {
                  "fixed": "2998147b59c9df0a51477c7a6b3d1f0ba3127dd4"
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          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-98303.json"
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          "ranges": [
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              "type": "ECOSYSTEM",
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                  "introduced": "2.6.25"
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            {
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                  "introduced": "6.7.0"
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                {
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                  "introduced": "6.13.0"
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                  "introduced": "6.19.0"
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          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-98303.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:52.334589366Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/06083cea4a3b95f5ebc85312f97d7086e6c9e782",
        "https://git.kernel.org/stable/c/1af2d87964d87ba7626d96928d68c09158b5a223",
        "https://git.kernel.org/stable/c/2998147b59c9df0a51477c7a6b3d1f0ba3127dd4",
        "https://git.kernel.org/stable/c/83aa83f81a8fec30ff5372dee60b2f0561bcb2ca",
        "https://git.kernel.org/stable/c/cac69c50716c712ef0114837c9427da66066124c",
        "https://git.kernel.org/stable/c/fda3000147dc96c75ba162f680bec0a9fecf3037",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98303.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-98303",
        "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-2026-98303.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-98303",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 521332,
  "published_at": "2026-10-06T08:46:00.524+00:00"
}