FKIE_CVE-2026-53012

Vulnerability from fkie_nvd - Published: 2026-06-24 17:17 - Updated: 2026-07-14 17:40
Severity
5.5 (Medium) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: nexthop: fix IPv6 route referencing IPv4 nexthop syzbot reported a panic [1] [2]. When an IPv6 nexthop is replaced with an IPv4 nexthop, the has_v4 flag of all groups containing this nexthop is not updated. This is because nh_group_v4_update is only called when replacing AF_INET to AF_INET6, but the reverse direction (AF_INET6 to AF_INET) is missed. This allows a stale has_v4=false to bypass fib6_check_nexthop, causing IPv6 routes to be attached to groups that effectively contain only AF_INET members. Subsequent route lookups then call nexthop_fib6_nh() which returns NULL for the AF_INET member, leading to a NULL pointer dereference. Fix by calling nh_group_v4_update whenever the family changes, not just AF_INET to AF_INET6. Reproducer: # AF_INET6 blackhole ip -6 nexthop add id 1 blackhole # group with has_v4=false ip nexthop add id 100 group 1 # replace with AF_INET (no -6), has_v4 stays false ip nexthop replace id 1 blackhole # pass stale has_v4 check ip -6 route add 2001:db8::/64 nhid 100 # panic ping -6 2001:db8::1 [1] https://syzkaller.appspot.com/bug?id=e17283eb2f8dcf3dd9b47fe6f67a95f71faadad0 [2] https://syzkaller.appspot.com/bug?id=8699b6ae54c9f35837d925686208402949e12ef3
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/29c95185ba32b621fbc3800fb86e7dc3edf5c2bePatch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/613c8f4a501421dd258b07ea614205d4e16ec845Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/6275796f22bb382f3e9aa58ed0b4ef7bdad78cb8Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/9c2d6770a5f4545a307eb66979bef7656a34d621Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/aaac3bed034239e1d75732211d9b05f30b0b4f35Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/ad85961004fd4bd2f31209ac4b07612c6cefb9e7Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/b3b7e850e1541f0520c4a12ec884255c30427ff6Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/ceffe81a0be92afc0cd1340bc8ca46559cce9bb4Patch
Impacted products
Vendor Product Version
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
To clipboard 

{
  "affected": [
    {
      "affectedData": [
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          "product": "Linux",
          "programFiles": [
            "net/ipv4/nexthop.c"
          ],
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      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
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  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnexthop: fix IPv6 route referencing IPv4 nexthop\n\nsyzbot reported a panic [1] [2].\n\nWhen an IPv6 nexthop is replaced with an IPv4 nexthop, the has_v4 flag\nof all groups containing this nexthop is not updated. This is because\nnh_group_v4_update is only called when replacing AF_INET to AF_INET6,\nbut the reverse direction (AF_INET6 to AF_INET) is missed.\n\nThis allows a stale has_v4=false to bypass fib6_check_nexthop, causing\nIPv6 routes to be attached to groups that effectively contain only AF_INET\nmembers. Subsequent route lookups then call nexthop_fib6_nh() which\nreturns NULL for the AF_INET member, leading to a NULL pointer\ndereference.\n\nFix by calling nh_group_v4_update whenever the family changes, not just\nAF_INET to AF_INET6.\n\nReproducer:\n\t# AF_INET6 blackhole\n\tip -6 nexthop add id 1 blackhole\n\t# group with has_v4=false\n\tip nexthop add id 100 group 1\n\t# replace with AF_INET (no -6), has_v4 stays false\n\tip nexthop replace id 1 blackhole\n\t# pass stale has_v4 check\n\tip -6 route add 2001:db8::/64 nhid 100\n\t# panic\n\tping -6 2001:db8::1\n\n[1] https://syzkaller.appspot.com/bug?id=e17283eb2f8dcf3dd9b47fe6f67a95f71faadad0\n[2] https://syzkaller.appspot.com/bug?id=8699b6ae54c9f35837d925686208402949e12ef3"
    }
  ],
  "id": "CVE-2026-53012",
  "lastModified": "2026-07-14T17:40:44.547",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "LOCAL",
          "availabilityImpact": "HIGH",
          "baseScore": 5.5,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "privilegesRequired": "LOW",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 1.8,
        "impactScore": 3.6,
        "source": "nvd@nist.gov",
        "type": "Primary"
      }
    ]
  },
  "published": "2026-06-24T17:17:12.433",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "tags": [
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      "url": "https://git.kernel.org/stable/c/29c95185ba32b621fbc3800fb86e7dc3edf5c2be"
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      "url": "https://git.kernel.org/stable/c/9c2d6770a5f4545a307eb66979bef7656a34d621"
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    {
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      "url": "https://git.kernel.org/stable/c/aaac3bed034239e1d75732211d9b05f30b0b4f35"
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    {
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    },
    {
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      "url": "https://git.kernel.org/stable/c/b3b7e850e1541f0520c4a12ec884255c30427ff6"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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      "url": "https://git.kernel.org/stable/c/ceffe81a0be92afc0cd1340bc8ca46559cce9bb4"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-476"
        }
      ],
      "source": "nvd@nist.gov",
      "type": "Primary"
    }
  ]
}



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  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
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  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


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