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CVE-2026-23340 (GCVE-0-2026-23340)

Vulnerability from cvelistv5 – Published: 2026-03-25 10:27 – Updated: 2026-09-08 08:45
VLAI
Title
net: sched: avoid qdisc_reset_all_tx_gt() vs dequeue race for lockless qdiscs
Summary
In the Linux kernel, the following vulnerability has been resolved: net: sched: avoid qdisc_reset_all_tx_gt() vs dequeue race for lockless qdiscs When shrinking the number of real tx queues, netif_set_real_num_tx_queues() calls qdisc_reset_all_tx_gt() to flush qdiscs for queues which will no longer be used. qdisc_reset_all_tx_gt() currently serializes qdisc_reset() with qdisc_lock(). However, for lockless qdiscs, the dequeue path is serialized by qdisc_run_begin/end() using qdisc->seqlock instead, so qdisc_reset() can run concurrently with __qdisc_run() and free skbs while they are still being dequeued, leading to UAF. This can easily be reproduced on e.g. virtio-net by imposing heavy traffic while frequently changing the number of queue pairs: iperf3 -ub0 -c $peer -t 0 & while :; do ethtool -L eth0 combined 1 ethtool -L eth0 combined 2 done With KASAN enabled, this leads to reports like: BUG: KASAN: slab-use-after-free in __qdisc_run+0x133f/0x1760 ... Call Trace: <TASK> ... __qdisc_run+0x133f/0x1760 __dev_queue_xmit+0x248f/0x3550 ip_finish_output2+0xa42/0x2110 ip_output+0x1a7/0x410 ip_send_skb+0x2e6/0x480 udp_send_skb+0xb0a/0x1590 udp_sendmsg+0x13c9/0x1fc0 ... </TASK> Allocated by task 1270 on cpu 5 at 44.558414s: ... alloc_skb_with_frags+0x84/0x7c0 sock_alloc_send_pskb+0x69a/0x830 __ip_append_data+0x1b86/0x48c0 ip_make_skb+0x1e8/0x2b0 udp_sendmsg+0x13a6/0x1fc0 ... Freed by task 1306 on cpu 3 at 44.558445s: ... kmem_cache_free+0x117/0x5e0 pfifo_fast_reset+0x14d/0x580 qdisc_reset+0x9e/0x5f0 netif_set_real_num_tx_queues+0x303/0x840 virtnet_set_channels+0x1bf/0x260 [virtio_net] ethnl_set_channels+0x684/0xae0 ethnl_default_set_doit+0x31a/0x890 ... Serialize qdisc_reset_all_tx_gt() against the lockless dequeue path by taking qdisc->seqlock for TCQ_F_NOLOCK qdiscs, matching the serialization model already used by dev_reset_queue(). Additionally clear QDISC_STATE_NON_EMPTY after reset so the qdisc state reflects an empty queue, avoiding needless re-scheduling.
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 6b3ba9146fe64b9bebb6346c9dcfe3b4851de2d7 , < 5bb27ad54d12de67e457d7d251198e361bef835e (git)
Affected: 6b3ba9146fe64b9bebb6346c9dcfe3b4851de2d7 , < 7594467c49bfc2f4644dee0415ac2290db11fa0d (git)
Affected: 6b3ba9146fe64b9bebb6346c9dcfe3b4851de2d7 , < dbd58b0730aa06ab6ad26079cf9a5b6b58e7e750 (git)
Affected: 6b3ba9146fe64b9bebb6346c9dcfe3b4851de2d7 , < 5bc4e69306ed7ae02232eb4c0b23ed621a26d504 (git)
Affected: 6b3ba9146fe64b9bebb6346c9dcfe3b4851de2d7 , < 8314944cc3bdeaa5a73e6f8a8cf0d94822e625cb (git)
Affected: 6b3ba9146fe64b9bebb6346c9dcfe3b4851de2d7 , < c69df4e0524f8de8e176ba389acd83e85f5f49d0 (git)
Affected: 6b3ba9146fe64b9bebb6346c9dcfe3b4851de2d7 , < 7f083faf59d14c04e01ec05a7507f036c965acf8 (git)
guessed Create a notification for this product.
Linux Linux Affected: 4.16
Unaffected: 0 , < 4.16 (semver)
Unaffected: 5.15.203 , ≤ 5.15.* (semver)
Unaffected: 6.1.167 , ≤ 6.1.* (semver)
Unaffected: 6.6.130 , ≤ 6.6.* (semver)
Unaffected: 6.12.77 , ≤ 6.12.* (semver)
Unaffected: 6.18.17 , ≤ 6.18.* (semver)
Unaffected: 6.19.7 , ≤ 6.19.* (semver)
Unaffected: 7.0 , ≤ * (original_commit_for_fix)
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Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP Affected: V3.1.6 , < * (custom)
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Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP Affected: V3.1.5 , < * (custom)
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Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP Affected: V3.1.6 , < * (custom)
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Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP Affected: V3.1.5 , < * (custom)
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Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP Affected: V3.1.6 , < * (custom)
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Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP Affected: V3.1.5 , < * (custom)
guessed Create a notification for this product.
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: sched: avoid qdisc_reset_all_tx_gt() vs dequeue race for lockless qdiscs\n\nWhen shrinking the number of real tx queues,\nnetif_set_real_num_tx_queues() calls qdisc_reset_all_tx_gt() to flush\nqdiscs for queues which will no longer be used.\n\nqdisc_reset_all_tx_gt() currently serializes qdisc_reset() with\nqdisc_lock(). However, for lockless qdiscs, the dequeue path is\nserialized by qdisc_run_begin/end() using qdisc-\u003eseqlock instead, so\nqdisc_reset() can run concurrently with __qdisc_run() and free skbs\nwhile they are still being dequeued, leading to UAF.\n\nThis can easily be reproduced on e.g. virtio-net by imposing heavy\ntraffic while frequently changing the number of queue pairs:\n\n  iperf3 -ub0 -c $peer -t 0 \u0026\n  while :; do\n    ethtool -L eth0 combined 1\n    ethtool -L eth0 combined 2\n  done\n\nWith KASAN enabled, this leads to reports like:\n\n  BUG: KASAN: slab-use-after-free in __qdisc_run+0x133f/0x1760\n  ...\n  Call Trace:\n   \u003cTASK\u003e\n   ...\n   __qdisc_run+0x133f/0x1760\n   __dev_queue_xmit+0x248f/0x3550\n   ip_finish_output2+0xa42/0x2110\n   ip_output+0x1a7/0x410\n   ip_send_skb+0x2e6/0x480\n   udp_send_skb+0xb0a/0x1590\n   udp_sendmsg+0x13c9/0x1fc0\n   ...\n   \u003c/TASK\u003e\n\n  Allocated by task 1270 on cpu 5 at 44.558414s:\n   ...\n   alloc_skb_with_frags+0x84/0x7c0\n   sock_alloc_send_pskb+0x69a/0x830\n   __ip_append_data+0x1b86/0x48c0\n   ip_make_skb+0x1e8/0x2b0\n   udp_sendmsg+0x13a6/0x1fc0\n   ...\n\n  Freed by task 1306 on cpu 3 at 44.558445s:\n   ...\n   kmem_cache_free+0x117/0x5e0\n   pfifo_fast_reset+0x14d/0x580\n   qdisc_reset+0x9e/0x5f0\n   netif_set_real_num_tx_queues+0x303/0x840\n   virtnet_set_channels+0x1bf/0x260 [virtio_net]\n   ethnl_set_channels+0x684/0xae0\n   ethnl_default_set_doit+0x31a/0x890\n   ...\n\nSerialize qdisc_reset_all_tx_gt() against the lockless dequeue path by\ntaking qdisc-\u003eseqlock for TCQ_F_NOLOCK qdiscs, matching the\nserialization model already used by dev_reset_queue().\n\nAdditionally clear QDISC_STATE_NON_EMPTY after reset so the qdisc state\nreflects an empty queue, avoiding needless re-scheduling."
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              "value": "AV:L - Triggered via ethtool netlink (ETHTOOL_MSG_CHANNELS_SET) which requires local access through a netlink socket. Not reachable from the network.\nAC:L - The attacker controls both sides of the race \u2014 sending traffic and changing channel count simultaneously. The commit message confirms this is \"easily reproduced\" with concurrent iperf and ethtool.\nPR:L - ETHTOOL_MSG_CHANNELS_SET uses GENL_UNS_ADMIN_PERM, which checks CAP_NET_ADMIN in the user namespace via netlink_ns_capable(). Veth devices support set_channels and can be created in user namespaces, so an unprivileged user can trigger this via unshare -Urn.\nUI:N - No user interaction is required. The attacker can independently trigger both the traffic and channel reconfiguration.\nS:U - Standard kernel use-after-free within the same security authority (kernel). No cross-boundary impact like VM escape.\nC:H - This is a use-after-free on sk_buff objects. The freed skb memory can be reallocated with attacker-controlled content, enabling reading of arbitrary kernel memory through the dangling pointer.\nI:H - UAF on sk_buff objects allows heap spraying \u2014 the freed skb slab can be reclaimed with attacker-controlled data, enabling arbitrary write primitives and potential code execution.\nA:H - The KASAN report confirms a slab-use-after-free crash in __qdisc_run. This causes a kernel oops/panic, and is easily and repeatedly triggerable."
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        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: sched: avoid qdisc_reset_all_tx_gt() vs dequeue race for lockless qdiscs\n\nWhen shrinking the number of real tx queues,\nnetif_set_real_num_tx_queues() calls qdisc_reset_all_tx_gt() to flush\nqdiscs for queues which will no longer be used.\n\nqdisc_reset_all_tx_gt() currently serializes qdisc_reset() with\nqdisc_lock(). However, for lockless qdiscs, the dequeue path is\nserialized by qdisc_run_begin/end() using qdisc-\u003eseqlock instead, so\nqdisc_reset() can run concurrently with __qdisc_run() and free skbs\nwhile they are still being dequeued, leading to UAF.\n\nThis can easily be reproduced on e.g. virtio-net by imposing heavy\ntraffic while frequently changing the number of queue pairs:\n\n  iperf3 -ub0 -c $peer -t 0 \u0026\n  while :; do\n    ethtool -L eth0 combined 1\n    ethtool -L eth0 combined 2\n  done\n\nWith KASAN enabled, this leads to reports like:\n\n  BUG: KASAN: slab-use-after-free in __qdisc_run+0x133f/0x1760\n  ...\n  Call Trace:\n   \u003cTASK\u003e\n   ...\n   __qdisc_run+0x133f/0x1760\n   __dev_queue_xmit+0x248f/0x3550\n   ip_finish_output2+0xa42/0x2110\n   ip_output+0x1a7/0x410\n   ip_send_skb+0x2e6/0x480\n   udp_send_skb+0xb0a/0x1590\n   udp_sendmsg+0x13c9/0x1fc0\n   ...\n   \u003c/TASK\u003e\n\n  Allocated by task 1270 on cpu 5 at 44.558414s:\n   ...\n   alloc_skb_with_frags+0x84/0x7c0\n   sock_alloc_send_pskb+0x69a/0x830\n   __ip_append_data+0x1b86/0x48c0\n   ip_make_skb+0x1e8/0x2b0\n   udp_sendmsg+0x13a6/0x1fc0\n   ...\n\n  Freed by task 1306 on cpu 3 at 44.558445s:\n   ...\n   kmem_cache_free+0x117/0x5e0\n   pfifo_fast_reset+0x14d/0x580\n   qdisc_reset+0x9e/0x5f0\n   netif_set_real_num_tx_queues+0x303/0x840\n   virtnet_set_channels+0x1bf/0x260 [virtio_net]\n   ethnl_set_channels+0x684/0xae0\n   ethnl_default_set_doit+0x31a/0x890\n   ...\n\nSerialize qdisc_reset_all_tx_gt() against the lockless dequeue path by\ntaking qdisc-\u003eseqlock for TCQ_F_NOLOCK qdiscs, matching the\nserialization model already used by dev_reset_queue().\n\nAdditionally clear QDISC_STATE_NON_EMPTY after reset so the qdisc state\nreflects an empty queue, avoiding needless re-scheduling."
          },
          {
            "lang": "es",
            "value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad:\n\nnet: sched: evitar la condici\u00f3n de carrera entre qdisc_reset_all_tx_gt() y la eliminaci\u00f3n de la cola para qdiscs sin bloqueo\n\nAl reducir el n\u00famero de colas de transmisi\u00f3n (tx) reales, netif_set_real_num_tx_queues() llama a qdisc_reset_all_tx_gt() para vaciar los qdiscs de las colas que ya no se utilizar\u00e1n.\n\nActualmente, qdisc_reset_all_tx_gt() serializa qdisc_reset() con qdisc_lock(). Sin embargo, para los qdiscs sin bloqueo, la ruta de eliminaci\u00f3n de la cola se serializa mediante qdisc_run_begin/end() usando qdisc-\u0026gt;seqlock en su lugar, por lo que qdisc_reset() puede ejecutarse concurrentemente con __qdisc_run() y liberar skbs mientras a\u00fan se est\u00e1n eliminando de la cola, lo que lleva a un uso despu\u00e9s de liberaci\u00f3n.\n\nEsto se puede reproducir f\u00e1cilmente, por ejemplo, en virtio-net, imponiendo un tr\u00e1fico intenso mientras se cambia frecuentemente el n\u00famero de pares de colas:\n\n  iperf3 -ub0 -c $peer -t 0 \u0026amp;\n  while :; do\n    ethtool -L eth0 combined 1\n    ethtool -L eth0 combined 2\n  done\n\nCon KASAN habilitado, esto lleva a informes como:\n\n  BUG: KASAN: uso despu\u00e9s de liberaci\u00f3n de slab en __qdisc_run+0x133f/0x1760\n  ...\n  Rastro de Llamada:\n   \n   ...\n   __qdisc_run+0x133f/0x1760\n   __dev_queue_xmit+0x248f/0x3550\n   ip_finish_output2+0xa42/0x2110\n   ip_output+0x1a7/0x410\n   ip_send_skb+0x2e6/0x480\n   udp_send_skb+0xb0a/0x1590\n   udp_sendmsg+0x13c9/0x1fc0\n   ...\n   \n\n  Asignado por la tarea 1270 en la cpu 5 a los 44.558414s:\n   ...\n   alloc_skb_with_frags+0x84/0x7c0\n   sock_alloc_send_pskb+0x69a/0x830\n   __ip_append_data+0x1b86/0x48c0\n   ip_make_skb+0x1e8/0x2b0\n   udp_sendmsg+0x13a6/0x1fc0\n   ...\n\n  Liberado por la tarea 1306 en la cpu 3 a los 44.558445s:\n   ...\n   kmem_cache_free+0x117/0x5e0\n   pfifo_fast_reset+0x14d/0x580\n   qdisc_reset+0x9e/0x5f0\n   netif_set_real_num_tx_queues+0x303/0x840\n   virtnet_set_channels+0x1bf/0x260 [virtio_net]\n   ethnl_set_channels+0x684/0xae0\n   ethnl_default_set_doit+0x31a/0x890\n   ...\n\nSerializar qdisc_reset_all_tx_gt() contra la ruta de eliminaci\u00f3n de la cola sin bloqueo tomando qdisc-\u0026gt;seqlock para los qdiscs TCQ_F_NOLOCK, coincidiendo con el modelo de serializaci\u00f3n ya utilizado por dev_reset_queue().\n\nAdem\u00e1s, borrar QDISC_STATE_NON_EMPTY despu\u00e9s del reinicio para que el estado del qdisc refleje una cola vac\u00eda, evitando una reprogramaci\u00f3n innecesaria."
          }
        ],
        "id": "CVE-2026-23340",
        "lastModified": "2026-07-14T13:18:30.280",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "LOCAL",
                "availabilityImpact": "HIGH",
                "baseScore": 7.8,
                "baseSeverity": "HIGH",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "LOW",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
                "version": "3.1"
              },
              "exploitabilityScore": 1.8,
              "impactScore": 5.9,
              "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
              "type": "Secondary"
            }
          ]
        },
        "published": "2026-03-25T11:16:31.837",
        "references": [
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "tags": [
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            "url": "https://git.kernel.org/stable/c/5bb27ad54d12de67e457d7d251198e361bef835e"
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          },
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            "source": "0b142b55-0307-4c5a-b3c9-f314f3fb7c5e",
            "url": "https://cert-portal.siemens.com/productcert/html/ssa-019113.html"
          },
          {
            "source": "0b142b55-0307-4c5a-b3c9-f314f3fb7c5e",
            "url": "https://cert-portal.siemens.com/productcert/html/ssa-082556.html"
          }
        ],
        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Modified",
        "weaknesses": [
          {
            "description": [
              {
                "lang": "en",
                "value": "CWE-416"
              }
            ],
            "source": "nvd@nist.gov",
            "type": "Primary"
          }
        ]
      }
    },
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-07-02T17:12:34+00:00",
      "cve": "CVE-2026-23340",
      "id": "CVE-2026-23340",
      "initial_release_date": "2026-03-25T00:00:00+00:00",
      "product_status:known_affected": "246",
      "product_status:known_not_affected": "28",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: net: sched: avoid qdisc_reset_all_tx_gt() vs dequeue race for lockless qdiscs",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-23340.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "moderate",
      "current_release_date": "2026-09-11T01:37:05Z",
      "cve": "CVE-2026-23340",
      "id": "CVE-2026-23340",
      "initial_release_date": "2026-03-25T16:56:00Z",
      "product_status:first_fixed": "2",
      "product_status:known_affected": "247",
      "product_status:known_not_affected": "62",
      "product_status:recommended": "303",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-23340",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-23340.json",
      "version": "20"
    }
  }
}



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Taxonomy of the tags.





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.

Sightings

Author Source Type Date Other

Nomenclature

  • 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.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • 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.


Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.