CVE-2026-23300 (GCVE-0-2026-23300)

Vulnerability from cvelistv5 – Published: 2026-03-25 10:26 – Updated: 2026-04-18 08:57
VLAI?
Title
net: ipv6: fix panic when IPv4 route references loopback IPv6 nexthop
Summary
In the Linux kernel, the following vulnerability has been resolved: net: ipv6: fix panic when IPv4 route references loopback IPv6 nexthop When a standalone IPv6 nexthop object is created with a loopback device (e.g., "ip -6 nexthop add id 100 dev lo"), fib6_nh_init() misclassifies it as a reject route. This is because nexthop objects have no destination prefix (fc_dst=::), causing fib6_is_reject() to match any loopback nexthop. The reject path skips fib_nh_common_init(), leaving nhc_pcpu_rth_output unallocated. If an IPv4 route later references this nexthop, __mkroute_output() dereferences NULL nhc_pcpu_rth_output and panics. Simplify the check in fib6_nh_init() to only match explicit reject routes (RTF_REJECT) instead of using fib6_is_reject(). The loopback promotion heuristic in fib6_is_reject() is handled separately by ip6_route_info_create_nh(). After this change, the three cases behave as follows: 1. Explicit reject route ("ip -6 route add unreachable 2001:db8::/64"): RTF_REJECT is set, enters reject path, skips fib_nh_common_init(). No behavior change. 2. Implicit loopback reject route ("ip -6 route add 2001:db8::/32 dev lo"): RTF_REJECT is not set, takes normal path, fib_nh_common_init() is called. ip6_route_info_create_nh() still promotes it to reject afterward. nhc_pcpu_rth_output is allocated but unused, which is harmless. 3. Standalone nexthop object ("ip -6 nexthop add id 100 dev lo"): RTF_REJECT is not set, takes normal path, fib_nh_common_init() is called. nhc_pcpu_rth_output is properly allocated, fixing the crash when IPv4 routes reference this nexthop.
Severity ?
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 493ced1ac47c48bb86d9d4e8e87df8592be85a0e , < 607e68c1b7c5a30c795571be1906d716e989a644 (git)
Affected: 493ced1ac47c48bb86d9d4e8e87df8592be85a0e , < c11d7c56c2076ee9cd72004f1976fe0734df2ae9 (git)
Affected: 493ced1ac47c48bb86d9d4e8e87df8592be85a0e , < b5062fc2150614c9ea8a611c2e0cb6e047ebfa3a (git)
Affected: 493ced1ac47c48bb86d9d4e8e87df8592be85a0e , < b299121e7453d23faddf464087dff513a495b4fc (git)
Affected: 493ced1ac47c48bb86d9d4e8e87df8592be85a0e , < f7c9f8e3607440fe39300efbaf46cf7b5eecb23f (git)
Affected: 493ced1ac47c48bb86d9d4e8e87df8592be85a0e , < b3b5a037d520afe3d5276e653bc0ff516bbda34c (git)
Affected: 493ced1ac47c48bb86d9d4e8e87df8592be85a0e , < 8650db85b4259d2885d2a80fbc2317ce24194133 (git)
Affected: 493ced1ac47c48bb86d9d4e8e87df8592be85a0e , < 21ec92774d1536f71bdc90b0e3d052eff99cf093 (git)
Create a notification for this product.
    Linux Linux Affected: 5.3
Unaffected: 0 , < 5.3 (semver)
Unaffected: 5.10.253 , ≤ 5.10.* (semver)
Unaffected: 5.15.203 , ≤ 5.15.* (semver)
Unaffected: 6.1.167 , ≤ 6.1.* (semver)
Unaffected: 6.6.130 , ≤ 6.6.* (semver)
Unaffected: 6.12.77 , ≤ 6.12.* (semver)
Unaffected: 6.18.17 , ≤ 6.18.* (semver)
Unaffected: 6.19.7 , ≤ 6.19.* (semver)
Unaffected: 7.0 , ≤ * (original_commit_for_fix)
Create a notification for this product.
Show details on NVD website
To clipboard 

{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/ipv6/route.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "607e68c1b7c5a30c795571be1906d716e989a644",
              "status": "affected",
              "version": "493ced1ac47c48bb86d9d4e8e87df8592be85a0e",
              "versionType": "git"
            },
            {
              "lessThan": "c11d7c56c2076ee9cd72004f1976fe0734df2ae9",
              "status": "affected",
              "version": "493ced1ac47c48bb86d9d4e8e87df8592be85a0e",
              "versionType": "git"
            },
            {
              "lessThan": "b5062fc2150614c9ea8a611c2e0cb6e047ebfa3a",
              "status": "affected",
              "version": "493ced1ac47c48bb86d9d4e8e87df8592be85a0e",
              "versionType": "git"
            },
            {
              "lessThan": "b299121e7453d23faddf464087dff513a495b4fc",
              "status": "affected",
              "version": "493ced1ac47c48bb86d9d4e8e87df8592be85a0e",
              "versionType": "git"
            },
            {
              "lessThan": "f7c9f8e3607440fe39300efbaf46cf7b5eecb23f",
              "status": "affected",
              "version": "493ced1ac47c48bb86d9d4e8e87df8592be85a0e",
              "versionType": "git"
            },
            {
              "lessThan": "b3b5a037d520afe3d5276e653bc0ff516bbda34c",
              "status": "affected",
              "version": "493ced1ac47c48bb86d9d4e8e87df8592be85a0e",
              "versionType": "git"
            },
            {
              "lessThan": "8650db85b4259d2885d2a80fbc2317ce24194133",
              "status": "affected",
              "version": "493ced1ac47c48bb86d9d4e8e87df8592be85a0e",
              "versionType": "git"
            },
            {
              "lessThan": "21ec92774d1536f71bdc90b0e3d052eff99cf093",
              "status": "affected",
              "version": "493ced1ac47c48bb86d9d4e8e87df8592be85a0e",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "net/ipv6/route.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "5.3"
            },
            {
              "lessThan": "5.3",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.10.*",
              "status": "unaffected",
              "version": "5.10.253",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.203",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.167",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.130",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.77",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.17",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.19.*",
              "status": "unaffected",
              "version": "6.19.7",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.0",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "5.10.253",
                  "versionStartIncluding": "5.3",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "5.15.203",
                  "versionStartIncluding": "5.3",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.1.167",
                  "versionStartIncluding": "5.3",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.6.130",
                  "versionStartIncluding": "5.3",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.77",
                  "versionStartIncluding": "5.3",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.17",
                  "versionStartIncluding": "5.3",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.19.7",
                  "versionStartIncluding": "5.3",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.0",
                  "versionStartIncluding": "5.3",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: ipv6: fix panic when IPv4 route references loopback IPv6 nexthop\n\nWhen a standalone IPv6 nexthop object is created with a loopback device\n(e.g., \"ip -6 nexthop add id 100 dev lo\"), fib6_nh_init() misclassifies\nit as a reject route. This is because nexthop objects have no destination\nprefix (fc_dst=::), causing fib6_is_reject() to match any loopback\nnexthop. The reject path skips fib_nh_common_init(), leaving\nnhc_pcpu_rth_output unallocated. If an IPv4 route later references this\nnexthop, __mkroute_output() dereferences NULL nhc_pcpu_rth_output and\npanics.\n\nSimplify the check in fib6_nh_init() to only match explicit reject\nroutes (RTF_REJECT) instead of using fib6_is_reject(). The loopback\npromotion heuristic in fib6_is_reject() is handled separately by\nip6_route_info_create_nh(). After this change, the three cases behave\nas follows:\n\n1. Explicit reject route (\"ip -6 route add unreachable 2001:db8::/64\"):\n   RTF_REJECT is set, enters reject path, skips fib_nh_common_init().\n   No behavior change.\n\n2. Implicit loopback reject route (\"ip -6 route add 2001:db8::/32 dev lo\"):\n   RTF_REJECT is not set, takes normal path, fib_nh_common_init() is\n   called. ip6_route_info_create_nh() still promotes it to reject\n   afterward. nhc_pcpu_rth_output is allocated but unused, which is\n   harmless.\n\n3. Standalone nexthop object (\"ip -6 nexthop add id 100 dev lo\"):\n   RTF_REJECT is not set, takes normal path, fib_nh_common_init() is\n   called. nhc_pcpu_rth_output is properly allocated, fixing the crash\n   when IPv4 routes reference this nexthop."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-04-18T08:57:47.517Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/607e68c1b7c5a30c795571be1906d716e989a644"
        },
        {
          "url": "https://git.kernel.org/stable/c/c11d7c56c2076ee9cd72004f1976fe0734df2ae9"
        },
        {
          "url": "https://git.kernel.org/stable/c/b5062fc2150614c9ea8a611c2e0cb6e047ebfa3a"
        },
        {
          "url": "https://git.kernel.org/stable/c/b299121e7453d23faddf464087dff513a495b4fc"
        },
        {
          "url": "https://git.kernel.org/stable/c/f7c9f8e3607440fe39300efbaf46cf7b5eecb23f"
        },
        {
          "url": "https://git.kernel.org/stable/c/b3b5a037d520afe3d5276e653bc0ff516bbda34c"
        },
        {
          "url": "https://git.kernel.org/stable/c/8650db85b4259d2885d2a80fbc2317ce24194133"
        },
        {
          "url": "https://git.kernel.org/stable/c/21ec92774d1536f71bdc90b0e3d052eff99cf093"
        }
      ],
      "title": "net: ipv6: fix panic when IPv4 route references loopback IPv6 nexthop",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-23300",
    "datePublished": "2026-03-25T10:26:56.138Z",
    "dateReserved": "2026-01-13T15:37:45.993Z",
    "dateUpdated": "2026-04-18T08:57:47.517Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-23300",
      "date": "2026-04-24",
      "epss": "0.00032",
      "percentile": "0.09294"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-23300\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-03-25T11:16:25.623\",\"lastModified\":\"2026-04-18T09:16:17.753\",\"vulnStatus\":\"Awaiting Analysis\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nnet: ipv6: fix panic when IPv4 route references loopback IPv6 nexthop\\n\\nWhen a standalone IPv6 nexthop object is created with a loopback device\\n(e.g., \\\"ip -6 nexthop add id 100 dev lo\\\"), fib6_nh_init() misclassifies\\nit as a reject route. This is because nexthop objects have no destination\\nprefix (fc_dst=::), causing fib6_is_reject() to match any loopback\\nnexthop. The reject path skips fib_nh_common_init(), leaving\\nnhc_pcpu_rth_output unallocated. If an IPv4 route later references this\\nnexthop, __mkroute_output() dereferences NULL nhc_pcpu_rth_output and\\npanics.\\n\\nSimplify the check in fib6_nh_init() to only match explicit reject\\nroutes (RTF_REJECT) instead of using fib6_is_reject(). The loopback\\npromotion heuristic in fib6_is_reject() is handled separately by\\nip6_route_info_create_nh(). After this change, the three cases behave\\nas follows:\\n\\n1. Explicit reject route (\\\"ip -6 route add unreachable 2001:db8::/64\\\"):\\n   RTF_REJECT is set, enters reject path, skips fib_nh_common_init().\\n   No behavior change.\\n\\n2. Implicit loopback reject route (\\\"ip -6 route add 2001:db8::/32 dev lo\\\"):\\n   RTF_REJECT is not set, takes normal path, fib_nh_common_init() is\\n   called. ip6_route_info_create_nh() still promotes it to reject\\n   afterward. nhc_pcpu_rth_output is allocated but unused, which is\\n   harmless.\\n\\n3. Standalone nexthop object (\\\"ip -6 nexthop add id 100 dev lo\\\"):\\n   RTF_REJECT is not set, takes normal path, fib_nh_common_init() is\\n   called. nhc_pcpu_rth_output is properly allocated, fixing the crash\\n   when IPv4 routes reference this nexthop.\"},{\"lang\":\"es\",\"value\":\"En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\\n\\nnet: ipv6: corrige el p\u00e1nico cuando una ruta IPv4 referencia un nexthop IPv6 de loopback\\n\\nCuando se crea un objeto nexthop IPv6 independiente con un dispositivo de loopback (p. ej., \u0027ip -6 nexthop add id 100 dev lo\u0027), fib6_nh_init() lo clasifica err\u00f3neamente como una ruta de rechazo. Esto se debe a que los objetos nexthop no tienen prefijo de destino (fc_dst=::), lo que hace que fib6_is_reject() coincida con cualquier nexthop de loopback. La ruta de rechazo omite fib_nh_common_init(), dejando nhc_pcpu_rth_output sin asignar. Si una ruta IPv4 referencia posteriormente este nexthop, __mkroute_output() desreferencia nhc_pcpu_rth_output NULL y entra en p\u00e1nico.\\n\\nSimplificar la verificaci\u00f3n en fib6_nh_init() para que solo coincida con rutas de rechazo expl\u00edcitas (RTF_REJECT) en lugar de usar fib6_is_reject(). La heur\u00edstica de promoci\u00f3n de loopback en fib6_is_reject() se maneja por separado por ip6_route_info_create_nh(). Despu\u00e9s de este cambio, los tres casos se comportan de la siguiente manera:\\n\\n1. Ruta de rechazo expl\u00edcita (\u0027ip -6 route add unreachable 2001:db8::/64\u0027):\\n   RTF_REJECT est\u00e1 configurado, entra en la ruta de rechazo, omite fib_nh_common_init().\\n   Sin cambio de comportamiento.\\n\\n2. Ruta de rechazo de loopback impl\u00edcita (\u0027ip -6 route add 2001:db8::/32 dev lo\u0027):\\n   RTF_REJECT no est\u00e1 configurado, toma la ruta normal, se llama a fib_nh_common_init().\\n   ip6_route_info_create_nh() a\u00fan lo promueve a rechazo posteriormente. nhc_pcpu_rth_output se asigna pero no se usa, lo cual es inofensivo.\\n\\n3. Objeto nexthop independiente (\u0027ip -6 nexthop add id 100 dev lo\u0027):\\n   RTF_REJECT no est\u00e1 configurado, toma la ruta normal, se llama a fib_nh_common_init().\\n   nhc_pcpu_rth_output se asigna correctamente, corrigiendo el fallo cuando las rutas IPv4 referencian este nexthop.\"}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/21ec92774d1536f71bdc90b0e3d052eff99cf093\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/607e68c1b7c5a30c795571be1906d716e989a644\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/8650db85b4259d2885d2a80fbc2317ce24194133\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/b299121e7453d23faddf464087dff513a495b4fc\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/b3b5a037d520afe3d5276e653bc0ff516bbda34c\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/b5062fc2150614c9ea8a611c2e0cb6e047ebfa3a\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/c11d7c56c2076ee9cd72004f1976fe0734df2ae9\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/f7c9f8e3607440fe39300efbaf46cf7b5eecb23f\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
  }
}


Log in or create an account to share your comment.




Tags
Taxonomy of the tags.




Sightings

Author Source Type Date

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



Detection rules are retrieved from Rulezet.