CVE-2026-64530 (GCVE-0-2026-64530)
Vulnerability from cvelistv5
Published
2026-07-26 06:28
Modified
2026-08-17 04:57
Severity ?
9.8 (Critical) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: net/sched: cls_api: Handle TC_ACT_CONSUMED in tcf_qevent_handle tcf_classify() can return TC_ACT_CONSUMED while the skb is held by the defragmentation engine (e.g. act_ct on out-of-order fragments). When that happens the skb is no longer owned by the caller and must not be touched again. tcf_qevent_handle() did not handle TC_ACT_CONSUMED: it fell through the switch and returned the skb to the caller as if classification had passed. The only qdisc that wires up qevents today is RED, via three call sites (qe_mark on RED_PROB_MARK/HARD_MARK, qe_early_drop on congestion_drop) red_enqueue() was continuing to operate on an skb it no longer owns in this case -- enqueueing it, dropping it, or updating statistics. Resulting in a UAF. tc qdisc add dev eth0 root handle 1: red ... qevent early_drop block 10 tc filter add block 10 ... action ct (with ct defrag enabled and traffic that produces out-of-order fragments, e.g. a fragmented UDP stream) Handle TC_ACT_CONSUMED in tcf_qevent_handle() the same way the ingress and egress fast paths do: treat it as stolen and return NULL without touching the skb. Unlike the TC_ACT_STOLEN case, the skb must not be dropped/freed here, as it is no longer owned by us.
References
Impacted products
Vendor Product Version
Linux Linux Version: 172ba7d46c202e679f3ccb10264c67416aaeb1c4
Version: 0b5b831122fc3789fff75be433ba3e4dd7b779d4
Version: 73f7da5fd124f2cda9161e2e46114915e6e82e97
Version: 3f14b377d01d8357eba032b4cabc8c1149b458b6
Version: 3f14b377d01d8357eba032b4cabc8c1149b458b6
Version: 3f14b377d01d8357eba032b4cabc8c1149b458b6
Version: 3f14b377d01d8357eba032b4cabc8c1149b458b6
Version: f5346df0591d10bc948761ca854b1fae6d2ef441
Version: 5.15.148   ≤
Version: 6.1.75   ≤
Version: 6.6.14   ≤
Version: 6.7.2   ≤
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/sched/cls_api.c"
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          "product": "Linux",
          "programFiles": [
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          ],
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      "cpeApplicability": [
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              "negate": false,
              "operator": "OR"
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      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: cls_api: Handle TC_ACT_CONSUMED in tcf_qevent_handle\n\ntcf_classify() can return TC_ACT_CONSUMED while the skb is held by the\ndefragmentation engine (e.g. act_ct on out-of-order fragments). When\nthat happens the skb is no longer owned by the caller and must not be\ntouched again.\n\ntcf_qevent_handle() did not handle TC_ACT_CONSUMED: it fell through the\nswitch and returned the skb to the caller as if classification had\npassed. The only qdisc that wires up qevents today is RED, via three call sites\n(qe_mark on RED_PROB_MARK/HARD_MARK, qe_early_drop on congestion_drop)\nred_enqueue() was continuing to operate on an skb it no longer owns  in this\ncase -- enqueueing it, dropping it, or updating statistics. Resulting in a UAF.\n\n  tc qdisc add dev eth0 root handle 1: red ... qevent early_drop block 10\n  tc filter add block 10 ... action ct\n\n  (with ct defrag enabled and traffic that produces out-of-order\n  fragments, e.g. a fragmented UDP stream)\n\nHandle TC_ACT_CONSUMED in tcf_qevent_handle() the same way the ingress\nand egress fast paths do: treat it as stolen and return NULL without\ntouching the skb. Unlike the TC_ACT_STOLEN case, the skb must not be\ndropped/freed here, as it is no longer owned by us."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 9.8,
            "baseSeverity": "CRITICAL",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - On a transparent bridge or traffic-shaping gateway configured with the RED qevent and act_ct, unauthenticated remote IP fragments reach red_enqueue() through normal receive, bridge-forwarding, and egress-qdisc processing. No local netlink access is required to trigger the deployed configuration.\nAC:L - The attacker controls fragment contents and ordering and can drive RED into deterministic hard-mark or drop conditions with sustained traffic. No race or condition outside the attacker\u0027s control must be won.\nPR:N - CAP_NET_ADMIN is required to create the vulnerable configuration, but a remote attacker sending fragments through an already configured appliance needs no privileges or authentication. Local triggering is also possible with namespaced CAP_NET_ADMIN.\nUI:N - Triggering requires only attacker-generated fragmented traffic and does not depend on a victim performing any action.\nS:U - The corruption occurs within the host kernel and compromises resources governed by that same security authority. This remains unchanged scope even when used for namespace escape or kernel privilege escalation.\nC:H - The reclaimable sk_buff use-after-free and corrupted defragmentation-tree links can be leveraged through attacker-controlled network heap spraying to disclose arbitrary kernel memory.\nI:H - RED overwrites linkage fields that overlap the defragmentation RB node and may free the object while it remains referenced, enabling subsequent writes through freed or attacker-reclaimed kernel objects and potential code execution.\nA:H - The dangling fragment-tree entry can cause immediate or deferred use-after-free, double-free, invalid tree operations, and kernel panic when another fragment arrives or the queue expires. The attacker can trigger this repeatedly with fragmented traffic."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-17T04:57:07.900Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/5ed3d6f85991656667059d3fa5a1d683ac58c447"
        },
        {
          "url": "https://git.kernel.org/stable/c/f42e8134a3a1074b834a574d404352f867ba994a"
        },
        {
          "url": "https://git.kernel.org/stable/c/447d493034a9cf7bf13a2abac86d0573d907ec2f"
        },
        {
          "url": "https://git.kernel.org/stable/c/e1270e69dcf2c3512c453484178f2e9dc0db3f05"
        },
        {
          "url": "https://git.kernel.org/stable/c/2140c2f3f2e7b066e1ae616ede8856cafd8015e9"
        },
        {
          "url": "https://git.kernel.org/stable/c/e28aedab9488343924d227b5a896faed67ce84d5"
        },
        {
          "url": "https://git.kernel.org/stable/c/a8a02897f2b479127db261de05cbf0c28b98d159"
        }
      ],
      "title": "net/sched: cls_api: Handle TC_ACT_CONSUMED in tcf_qevent_handle",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-64530",
    "datePublished": "2026-07-26T06:28:42.970Z",
    "dateReserved": "2026-07-19T15:36:31.794Z",
    "dateUpdated": "2026-08-17T04:57:07.900Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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