xfrm: fix ip_rt_bug race in icmp_route_lookup reverse path

{
  "id": "b2fe587f1b7ab4e5f5a45f8e945fb65ded8d8bedf8c8b5c08e7636d18c45f3dc",
  "url": "https://osv.dev/vulnerability/CVE-2026-45905",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "xfrm: fix ip_rt_bug race in icmp_route_lookup reverse path",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: xfrm: fix ip_rt_bug race in icmp_route_lookup reverse path icmp_route_lookup() performs multiple route lookups to find a suitable route for sending ICMP error messages, with special handling for XFRM (IPsec) policies. The lookup sequence is: 1. First, lookup output route for ICMP reply (dst = original src) 2. Pass through xfrm_lookup() for policy check 3. If blocked (-EPERM) or dst is not local, enter \"reverse path\" 4. In reverse path, call xfrm_decode_session_reverse() to get fl4_dec which reverses the original packet's flow (saddr<->daddr swapped) 5. If fl4_dec.saddr is local (we are the original destination), use __ip_route_output_key() for output route lookup 6. If fl4_dec.saddr is NOT local (we are a forwarding node), use ip_route_input() to simulate the reverse packet's input path 7. Finally, pass rt2 through xfrm_lookup() with XFRM_LOOKUP_ICMP flag The bug occurs in step 6: ip_route_input() is called with fl4_dec.daddr (original packet's source) as destination. If this address becomes local between the initial check and ip_route_input() call (e.g., due to concurrent \"ip addr add\"), ip_route_input() returns a LOCAL route with dst.output set to ip_rt_bug. This route is then used for ICMP output, causing dst_output() to call ip_rt_bug(), triggering a WARN_ON: ------------[ cut here ]------------ WARNING: net/ipv4/route.c:1275 at ip_rt_bug+0x21/0x30, CPU#1 Call Trace: ip_push_pending_frames+0x202/0x240 icm",
    "evidence": "osv:CVE-2026-45905",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.1.165",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.6.128",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.12.75",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.18.14",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.19.4",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2026-45905",
      "aliases": [
        "CVE-2026-45905"
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
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                {
                  "fixed": "9a95ec9144eeff1fc6fbcc21b677e322c6f1430b"
                },
                {
                  "fixed": "2c1f59005da9dd4b07b26984fd719e36557dc57c"
                },
                {
                  "fixed": "b04061f89ffc6168e7ec3c71d0086ec3c3797228"
                },
                {
                  "fixed": "1c9ef28f643cce34a6a6c36c8f4d6d60a60db7e1"
                },
                {
                  "fixed": "423ce12d10b426709489d6b84fdaa6d2f31c5652"
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                {
                  "fixed": "81b84de32bb27ae1ae2eb9acf0420e9d0d14bf00"
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              ]
            }
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          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-45905.json"
          }
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        {
          "ranges": [
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              "type": "ECOSYSTEM",
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                  "introduced": "2.6.25"
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                  "fixed": "6.1.165"
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                {
                  "introduced": "6.2.0"
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                {
                  "fixed": "6.6.128"
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              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.7.0"
                },
                {
                  "fixed": "6.12.75"
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            {
              "type": "ECOSYSTEM",
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                  "fixed": "6.19.4"
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          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-45905.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:39.970785869Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/1c9ef28f643cce34a6a6c36c8f4d6d60a60db7e1",
        "https://git.kernel.org/stable/c/2c1f59005da9dd4b07b26984fd719e36557dc57c",
        "https://git.kernel.org/stable/c/423ce12d10b426709489d6b84fdaa6d2f31c5652",
        "https://git.kernel.org/stable/c/81b84de32bb27ae1ae2eb9acf0420e9d0d14bf00",
        "https://git.kernel.org/stable/c/9a95ec9144eeff1fc6fbcc21b677e322c6f1430b",
        "https://git.kernel.org/stable/c/b04061f89ffc6168e7ec3c71d0086ec3c3797228",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/45xxx/CVE-2026-45905.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-45905",
        "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/2026/45xxx/CVE-2026-45905.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-45905",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 507412,
  "published_at": "2026-05-27T12:17:15.05+00:00"
}