CVE-2026-98303 (GCVE-0-2026-98303)
Vulnerability from cvelistv5
Published
2026-10-06 08:46
Modified
2026-10-19 09:17
Severity ?
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.
References
Impacted products
Vendor Product Version
Linux Linux Version: 8b7817f3a959ed99d7443afc12f78a7e1fcc2063
Version: 8b7817f3a959ed99d7443afc12f78a7e1fcc2063
Version: 8b7817f3a959ed99d7443afc12f78a7e1fcc2063
Version: 8b7817f3a959ed99d7443afc12f78a7e1fcc2063
Version: 8b7817f3a959ed99d7443afc12f78a7e1fcc2063
Version: 8b7817f3a959ed99d7443afc12f78a7e1fcc2063
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/ipv4/icmp.c"
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          "vendor": "Linux",
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              "status": "unaffected",
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              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix"
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        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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                  "vulnerable": true
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              "operator": "OR"
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nipv4: icmp: reject RTN_UNREACHABLE input routes in icmp_route_lookup\n\nWhen the forward output route cannot be used in icmp_route_lookup(),\nit enters the \"reverse path\" and calls ip_route_input() on fl4_dec.daddr,\nthe original packet\u0027s source address.\n\nip_route_input() only returns an error for truly invalid packets. For\nunreachable addresses it will succeed and return an input route whose\ndst.output is set to ip_rt_bug(). The existing check only rejects\nRTN_LOCAL routes, so the RTN_UNREACHABLE route types can still be returned\nand later used for output, syzkaller triggering a WARN_ON_ONCE()\nin ip_rt_bug() as bellow:\n\n ------------[ cut here ]------------\n WARNING: net/ipv4/route.c:1273 at ip_rt_bug+0x14/0x20\n RIP: 0010:ip_rt_bug+0x14/0x20\n Call Trace:\n  ip_push_pending_frames+0xfa/0x100\n  __icmp_send+0x905/0xf10\n  ip_options_compile+0xc0/0xd0\n  ip_rcv_finish_core+0x321/0xae0\n  ip_rcv+0x1de/0x260\n  __netif_receive_skb_one_core+0x11a/0x130\n  netif_receive_skb+0x7b/0x260\n  tun_get_user+0x11bf/0x1c10\n ------------[ cut here ]------------\n\nReject input route that is RTN_UNREACHABLE to fix it. The net warning\nis only printed for RTN_LOCAL, as RTN_UNREACHABLE is not the result of\na race condition."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T09:17:14.136Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/06083cea4a3b95f5ebc85312f97d7086e6c9e782"
        },
        {
          "url": "https://git.kernel.org/stable/c/83aa83f81a8fec30ff5372dee60b2f0561bcb2ca"
        },
        {
          "url": "https://git.kernel.org/stable/c/cac69c50716c712ef0114837c9427da66066124c"
        },
        {
          "url": "https://git.kernel.org/stable/c/1af2d87964d87ba7626d96928d68c09158b5a223"
        },
        {
          "url": "https://git.kernel.org/stable/c/fda3000147dc96c75ba162f680bec0a9fecf3037"
        },
        {
          "url": "https://git.kernel.org/stable/c/2998147b59c9df0a51477c7a6b3d1f0ba3127dd4"
        }
      ],
      "title": "ipv4: icmp: reject RTN_UNREACHABLE input routes in icmp_route_lookup",
      "x_generator": {
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      }
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  "cveMetadata": {
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-98303",
    "datePublished": "2026-10-06T08:46:00.524Z",
    "dateReserved": "2026-09-25T10:25:14.338Z",
    "dateUpdated": "2026-10-19T09:17:14.136Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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