FKIE_CVE-2026-74621

Vulnerability from fkie_nvd - Published: 2026-08-22 16:16 - Updated: 2026-10-14 13:10
Severity
7.5 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: net/sched: act_ct: fix sk_buff leak when the header checks reject a packet tcf_ct_handle_fragments() runs its header sanity checks before handing anything to the defragmentation engine: if (family == NFPROTO_IPV4) err = tcf_ct_ipv4_is_fragment(skb, &frag); else err = tcf_ct_ipv6_is_fragment(skb, &frag); if (err || !frag) return err; tcf_ct_ipv4_is_fragment() returns -EINVAL or -ENOMEM; tcf_ct_ipv6_is_fragment() adds -EPROTO when ipv6_find_hdr() fails. None of them frees or queues the skb, so on that path the caller still owns it. tcf_ct_act() however funnels every non-zero return into the ownership-transfer exit: err = tcf_ct_handle_fragments(net, skb, family, p->zone, &defrag); if (err) goto out_frag; ... out_frag: if (err != -EINPROGRESS) tcf_action_inc_drop_qstats(&c->common); return TC_ACT_CONSUMED; TC_ACT_CONSUMED means the action took ownership of the skb, so no caller frees it - sch_handle_ingress(), sch_handle_egress() and tcf_qevent_handle() all deliberately skip the free for that verdict. The skb is therefore orphaned: one sk_buff plus its data buffer is leaked per malformed packet, unbounded. Note the drop counter is already incremented for these errors, so the statistics claim a drop that never happens. Three different ownership states reach out_frag: today - the skb may be queued by the defrag engine (-EINPROGRESS), already freed by nf_ct_handle_fragments(), or still owned by us. Tell the caller which of those it is, and free the packet ourselves in the last case, which restores the TC_ACT_SHOT behaviour that predated the Fixes: commit. Reproduced on v7.2-rc6 with a 54-byte frame carrying a 40-byte IPv6 header with nexthdr = 0 (hop-by-hop) and nothing after it, on a clsact ingress chain with "action ct". kmemleak reports one leaked 232-byte skbuff_head_cache object plus its 704-byte data buffer per packet; with this patch it reports none.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/23e97d594ddd0153020c506d5041048fbde1beb4
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/439d3e404f9d5e515911cc8132cde198b337c19e
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/47d99828591d0fe8be4b9c8992ff3b8e47968db9
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/737873a59905a54ca0d2d127ef882f3f88bf4379
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/8a7ed561671aa6a911a2de99e59ef670a4d0b1df
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/b47bb899e04b5407c5a63fe88d4b6676586a6e84
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/b5dbecc2016e1692fd1c2532af9c41ba729cb747
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/sched/act_ct.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "b5dbecc2016e1692fd1c2532af9c41ba729cb747",
              "status": "affected",
              "version": "172ba7d46c202e679f3ccb10264c67416aaeb1c4",
              "versionType": "git"
            },
            {
              "lessThan": "23e97d594ddd0153020c506d5041048fbde1beb4",
              "status": "affected",
              "version": "0b5b831122fc3789fff75be433ba3e4dd7b779d4",
              "versionType": "git"
            },
            {
              "lessThan": "737873a59905a54ca0d2d127ef882f3f88bf4379",
              "status": "affected",
              "version": "73f7da5fd124f2cda9161e2e46114915e6e82e97",
              "versionType": "git"
            },
            {
              "lessThan": "47d99828591d0fe8be4b9c8992ff3b8e47968db9",
              "status": "affected",
              "version": "3f14b377d01d8357eba032b4cabc8c1149b458b6",
              "versionType": "git"
            },
            {
              "lessThan": "b47bb899e04b5407c5a63fe88d4b6676586a6e84",
              "status": "affected",
              "version": "3f14b377d01d8357eba032b4cabc8c1149b458b6",
              "versionType": "git"
            },
            {
              "lessThan": "439d3e404f9d5e515911cc8132cde198b337c19e",
              "status": "affected",
              "version": "3f14b377d01d8357eba032b4cabc8c1149b458b6",
              "versionType": "git"
            },
            {
              "lessThan": "8a7ed561671aa6a911a2de99e59ef670a4d0b1df",
              "status": "affected",
              "version": "3f14b377d01d8357eba032b4cabc8c1149b458b6",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "f5346df0591d10bc948761ca854b1fae6d2ef441",
              "versionType": "git"
            },
            {
              "lessThan": "5.15.217",
              "status": "affected",
              "version": "5.15.148",
              "versionType": "semver"
            },
            {
              "lessThan": "6.1.184",
              "status": "affected",
              "version": "6.1.75",
              "versionType": "semver"
            },
            {
              "lessThan": "6.6.152",
              "status": "affected",
              "version": "6.6.14",
              "versionType": "semver"
            },
            {
              "lessThan": "6.8",
              "status": "affected",
              "version": "6.7.2",
              "versionType": "semver"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "net/sched/act_ct.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.8"
            },
            {
              "lessThan": "6.8",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.217",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.184",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.152",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.104",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.45",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.1.*",
              "status": "unaffected",
              "version": "7.1.9",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: act_ct: fix sk_buff leak when the header checks reject a packet\n\ntcf_ct_handle_fragments() runs its header sanity checks before handing\nanything to the defragmentation engine:\n\n\tif (family == NFPROTO_IPV4)\n\t\terr = tcf_ct_ipv4_is_fragment(skb, \u0026frag);\n\telse\n\t\terr = tcf_ct_ipv6_is_fragment(skb, \u0026frag);\n\tif (err || !frag)\n\t\treturn err;\n\ntcf_ct_ipv4_is_fragment() returns -EINVAL or -ENOMEM;\ntcf_ct_ipv6_is_fragment() adds -EPROTO when ipv6_find_hdr() fails. None of\nthem frees or queues the skb, so on that path the caller still owns it.\n\ntcf_ct_act() however funnels every non-zero return into the\nownership-transfer exit:\n\n\terr = tcf_ct_handle_fragments(net, skb, family, p-\u003ezone, \u0026defrag);\n\tif (err)\n\t\tgoto out_frag;\n\t...\nout_frag:\n\tif (err != -EINPROGRESS)\n\t\ttcf_action_inc_drop_qstats(\u0026c-\u003ecommon);\n\treturn TC_ACT_CONSUMED;\n\nTC_ACT_CONSUMED means the action took ownership of the skb, so no caller\nfrees it - sch_handle_ingress(), sch_handle_egress() and\ntcf_qevent_handle() all deliberately skip the free for that verdict. The\nskb is therefore orphaned: one sk_buff plus its data buffer is leaked per\nmalformed packet, unbounded. Note the drop counter is already incremented\nfor these errors, so the statistics claim a drop that never happens.\n\nThree different ownership states reach out_frag: today - the skb may be\nqueued by the defrag engine (-EINPROGRESS), already freed by\nnf_ct_handle_fragments(), or still owned by us. Tell the caller which of\nthose it is, and free the packet ourselves in the last case, which\nrestores the TC_ACT_SHOT behaviour that predated the Fixes: commit.\n\nReproduced on v7.2-rc6 with a 54-byte frame carrying a 40-byte IPv6\nheader with nexthdr = 0 (hop-by-hop) and nothing after it, on a\nclsact ingress chain with \"action ct\". kmemleak reports one leaked\n232-byte skbuff_head_cache object plus its 704-byte data buffer per\npacket; with this patch it reports none."
    },
    {
      "lang": "es",
      "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nnet/sched: act_ct: corrige la fuga de sk_buff cuando las comprobaciones de cabecera rechazan un paquete\n\ntcf_ct_handle_fragments() ejecuta sus comprobaciones de integridad de cabecera antes de entregar cualquier cosa al motor de desfragmentaci\u00f3n:\n\n\tif (family == NFPROTO_IPV4)\n\t\terr = tcf_ct_ipv4_is_fragment(skb, \u0026frag);\n\telse\n\t\terr = tcf_ct_ipv6_is_fragment(skb, \u0026frag);\n\tif (err || !frag)\n\t\treturn err;\n\ntcf_ct_ipv4_is_fragment() devuelve -EINVAL o -ENOMEM;\ntcf_ct_ipv6_is_fragment() a\u00f1ade -EPROTO cuando ipv6_find_hdr() falla. Ninguno de ellos libera o encola el skb, por lo que en esa ruta el llamador todav\u00eda lo posee.\n\ntcf_ct_act() sin embargo canaliza cada retorno no nulo hacia la salida de transferencia de propiedad:\n\n\terr = tcf_ct_handle_fragments(net, skb, family, p -\u003e zone, \u0026defrag);\n\tif (err)\n\t\tgoto out_frag;\n\t...\nout_frag:\n\tif (err != -EINPROGRESS)\n\t\ttcf_action_inc_drop_qstats(\u0026c -\u003e common);\n\treturn TC_ACT_CONSUMED;\n\nTC_ACT_CONSUMED significa que la acci\u00f3n tom\u00f3 posesi\u00f3n del skb, por lo que ning\u00fan llamador lo libera - sch_handle_ingress(), sch_handle_egress() y tcf_qevent_handle() omiten deliberadamente la liberaci\u00f3n para ese veredicto. El skb queda, por lo tanto, hu\u00e9rfano: un sk_buff m\u00e1s su b\u00fafer de datos se fuga por cada paquete malformado, sin l\u00edmites. N\u00f3tese que el contador de ca\u00eddas ya se incrementa para estos errores, por lo que las estad\u00edsticas afirman una ca\u00edda que nunca ocurre.\n\nTres estados de propiedad diferentes alcanzan out_frag: hoy - el skb puede ser encolado por el motor de desfragmentaci\u00f3n (-EINPROGRESS), ya liberado por nf_ct_handle_fragments(), o todav\u00eda en nuestra posesi\u00f3n. Informar al llamador cu\u00e1l de ellos es, y liberar el paquete nosotros mismos en el \u00faltimo caso, lo que restaura el comportamiento TC_ACT_SHOT que precedi\u00f3 al commit de Fixes:.\n\nReproducido en v7.2-rc6 con una trama de 54 bytes que transporta una cabecera IPv6 de 40 bytes con nexthdr = 0 (salto a salto) y nada despu\u00e9s de ella, en una cadena de entrada clsact con \u0027action ct\u0027. kmemleak informa de un objeto skbuff_head_cache de 232 bytes fugado m\u00e1s su b\u00fafer de datos de 704 bytes por paquete; con este parche no informa de ninguno."
    }
  ],
  "id": "CVE-2026-74621",
  "lastModified": "2026-10-14T13:10:00.187",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "HIGH",
          "baseScore": 7.5,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 3.6,
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-08-22T16:16:34.897",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/23e97d594ddd0153020c506d5041048fbde1beb4"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/439d3e404f9d5e515911cc8132cde198b337c19e"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/47d99828591d0fe8be4b9c8992ff3b8e47968db9"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/737873a59905a54ca0d2d127ef882f3f88bf4379"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/8a7ed561671aa6a911a2de99e59ef670a4d0b1df"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/b47bb899e04b5407c5a63fe88d4b6676586a6e84"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/b5dbecc2016e1692fd1c2532af9c41ba729cb747"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



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