{
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        "ecosystem": "Linux",
        "name": "Kernel"
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  "database_specific": {
    "cna_assigner": "Linux",
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/74xxx/CVE-2026-74621.json"
  },
  "details": "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.",
  "id": "CVE-2026-74621",
  "modified": "2026-08-27T11:30:51.125191880Z",
  "published": "2026-08-22T15:32:04.990Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/23e97d594ddd0153020c506d5041048fbde1beb4"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/439d3e404f9d5e515911cc8132cde198b337c19e"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/47d99828591d0fe8be4b9c8992ff3b8e47968db9"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/737873a59905a54ca0d2d127ef882f3f88bf4379"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/8a7ed561671aa6a911a2de99e59ef670a4d0b1df"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/b47bb899e04b5407c5a63fe88d4b6676586a6e84"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/b5dbecc2016e1692fd1c2532af9c41ba729cb747"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/74xxx/CVE-2026-74621.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-74621"
    },
    {
      "type": "PACKAGE",
      "url": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
    }
  ],
  "schema_version": "1.9.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "net/sched: act_ct: fix sk_buff leak when the header checks reject a packet"
}