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CVE-2026-74264 (GCVE-0-2026-74264)

Vulnerability from cvelistv5 – Published: 2026-08-15 05:57 – Updated: 2026-08-17 05:45
VLAI
Title
net: watchdog: fix refcount tracking races
Summary
In the Linux kernel, the following vulnerability has been resolved: net: watchdog: fix refcount tracking races Blamed commit converted the untracked dev_hold()/dev_put() calls in the watchdog code to use the tracked dev_hold_track()/dev_put_track() (which were later renamed/interfaced to netdev_hold() and netdev_put()). By introducing dev->watchdog_dev_tracker to store the reference tracking information without adding synchronization between netdev_watchdog_up() and dev_watchdog(), it enabled the race condition where this pointer could be overwritten or freed concurrently, leading to the list corruption crash syzbot reported: list_del corruption, ffff888114a18c00->next is NULL kernel BUG at lib/list_debug.c:52 ! Oops: invalid opcode: 0000 [#1] SMP KASAN PTI CPU: 1 UID: 0 PID: 91 Comm: kworker/u8:5 Not tainted syzkaller #0 PREEMPT(lazy) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026 Workqueue: events_unbound linkwatch_event RIP: 0010:__list_del_entry_valid_or_report.cold+0x22/0x2a lib/list_debug.c:52 Call Trace: <TASK> __list_del_entry_valid include/linux/list.h:132 [inline] __list_del_entry include/linux/list.h:246 [inline] list_move_tail include/linux/list.h:341 [inline] ref_tracker_free+0x1a7/0x6c0 lib/ref_tracker.c:329 netdev_tracker_free include/linux/netdevice.h:4491 [inline] netdev_put include/linux/netdevice.h:4508 [inline] netdev_put include/linux/netdevice.h:4504 [inline] netdev_watchdog_down net/sched/sch_generic.c:600 [inline] dev_deactivate_many+0x28c/0xfe0 net/sched/sch_generic.c:1363 dev_deactivate+0x109/0x1d0 net/sched/sch_generic.c:1397 linkwatch_do_dev net/core/link_watch.c:184 [inline] linkwatch_do_dev+0xd3/0x120 net/core/link_watch.c:166 __linkwatch_run_queue+0x3a5/0x810 net/core/link_watch.c:240 linkwatch_event+0x8f/0xc0 net/core/link_watch.c:314 process_one_work+0xa0e/0x1980 kernel/workqueue.c:3314 process_scheduled_works kernel/workqueue.c:3397 [inline] worker_thread+0x5ef/0xe50 kernel/workqueue.c:3478 kthread+0x370/0x450 kernel/kthread.c:436 ret_from_fork+0x69a/0xc80 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 This patch has three coordinated parts: 1) Add dev->watchdog_lock and dev->watchdog_ref_held to serialize watchdog operations. 2) Remove netdev_watchdog_up() call from netif_carrier_on(): This ensures netdev_watchdog_up() is only called from process/BH context (via linkwatch workqueue dev_activate()), allowing us to use spin_lock_bh() for synchronization. 3) Synchronize watchdog up and watchdog timer: Protect netdev_watchdog_up() with tx_global_lock and watchdog_lock. Only allocate a new tracker in netdev_watchdog_up() if one is not already present. In dev_watchdog(), ensure we don't release the tracker if the timer was rescheduled either by dev_watchdog() itself or concurrently by netdev_watchdog_up().
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: f12bf6f3f942b37de65eeea8be25903587fec930 , < 446fe8ce699ce0a4d702f7b0fcdb50de340b9260 (git)
Affected: f12bf6f3f942b37de65eeea8be25903587fec930 , < 7ce2b00ff058ec4cafc9b447e1f0a6d6f49275d9 (git)
Affected: f12bf6f3f942b37de65eeea8be25903587fec930 , < 8eed5519e496b7a07f441a0f579cb228a33189f7 (git)
guessed Create a notification for this product.
Linux Linux Affected: 5.17
Unaffected: 0 , < 5.17 (semver)
Unaffected: 6.18.40 , ≤ 6.18.* (semver)
Unaffected: 7.1.5 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
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{
  "containers": {
    "cna": {
      "affected": [
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          "product": "Linux",
          "programFiles": [
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                  "vulnerable": true
                },
                {
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          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: watchdog: fix refcount tracking races\n\nBlamed commit converted the untracked dev_hold()/dev_put() calls\nin the watchdog code to use the tracked dev_hold_track()/dev_put_track()\n(which were later renamed/interfaced to netdev_hold() and netdev_put()).\n\nBy introducing dev-\u003ewatchdog_dev_tracker to store the\nreference tracking information without adding synchronization\nbetween netdev_watchdog_up() and dev_watchdog(), it enabled the\nrace condition where this pointer could be overwritten or freed\nconcurrently, leading to the list corruption crash syzbot reported:\n\nlist_del corruption, ffff888114a18c00-\u003enext is NULL\n kernel BUG at lib/list_debug.c:52 !\nOops: invalid opcode: 0000 [#1] SMP KASAN PTI\nCPU: 1 UID: 0 PID: 91 Comm: kworker/u8:5 Not tainted syzkaller #0 PREEMPT(lazy)\nHardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026\nWorkqueue: events_unbound linkwatch_event\n RIP: 0010:__list_del_entry_valid_or_report.cold+0x22/0x2a lib/list_debug.c:52\nCall Trace:\n \u003cTASK\u003e\n  __list_del_entry_valid include/linux/list.h:132 [inline]\n  __list_del_entry include/linux/list.h:246 [inline]\n  list_move_tail include/linux/list.h:341 [inline]\n  ref_tracker_free+0x1a7/0x6c0 lib/ref_tracker.c:329\n  netdev_tracker_free include/linux/netdevice.h:4491 [inline]\n  netdev_put include/linux/netdevice.h:4508 [inline]\n  netdev_put include/linux/netdevice.h:4504 [inline]\n  netdev_watchdog_down net/sched/sch_generic.c:600 [inline]\n  dev_deactivate_many+0x28c/0xfe0 net/sched/sch_generic.c:1363\n  dev_deactivate+0x109/0x1d0 net/sched/sch_generic.c:1397\n  linkwatch_do_dev net/core/link_watch.c:184 [inline]\n  linkwatch_do_dev+0xd3/0x120 net/core/link_watch.c:166\n  __linkwatch_run_queue+0x3a5/0x810 net/core/link_watch.c:240\n  linkwatch_event+0x8f/0xc0 net/core/link_watch.c:314\n  process_one_work+0xa0e/0x1980 kernel/workqueue.c:3314\n  process_scheduled_works kernel/workqueue.c:3397 [inline]\n  worker_thread+0x5ef/0xe50 kernel/workqueue.c:3478\n  kthread+0x370/0x450 kernel/kthread.c:436\n  ret_from_fork+0x69a/0xc80 arch/x86/kernel/process.c:158\n  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245\n\nThis patch has three coordinated parts:\n\n1) Add dev-\u003ewatchdog_lock and dev-\u003ewatchdog_ref_held to serialize watchdog operations.\n\n2) Remove netdev_watchdog_up() call from netif_carrier_on():\n   This ensures netdev_watchdog_up() is only called from process/BH context\n   (via linkwatch workqueue dev_activate()), allowing us to use\n   spin_lock_bh() for synchronization.\n\n3) Synchronize watchdog up and watchdog timer:\n   Protect netdev_watchdog_up() with tx_global_lock and watchdog_lock.\n   Only allocate a new tracker in netdev_watchdog_up() if one is\n   not already present.\n   In dev_watchdog(), ensure we don\u0027t release the tracker if the\n   timer was rescheduled either by dev_watchdog() itself or concurrently\n   by netdev_watchdog_up()."
        }
      ],
      "metrics": [
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            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The bug is in net/sched netdev watchdog refcount handling, reached via local carrier/linkwatch and rtnl-driven netdev lifecycle on TX-timeout-capable interfaces (virtio_net, Ethernet NICs), not by processing remote packets.\nAC:L - An attacker controls both sides of the race by concurrently driving carrier up/down transitions and TX watchdog timer expiry; syzbot reproduced this reliably without uncontrollable timing or layout dependencies.\nPR:L - Triggering netdev carrier activation/deactivation and watchdog setup on affected interfaces requires CAP_NET_ADMIN, obtainable by unprivileged users through user/network namespaces or as administrators in cloud VMs with virtio_net.\nUI:N - No victim interaction is required; exploitation needs only attacker-initiated interface churn and concurrent watchdog timer activity.\nS:U - Impact is kernel netdev refcount/tracker corruption within kernel memory; it does not by itself cross VM, container, or IOMMU security boundaries.\nC:H - Unsynchronized watchdog_dev_tracker allows concurrent free/overwrite (use-after-free/double-free) and ref_tracker list corruption, enabling arbitrary kernel memory disclosure.\nI:H - The same refcount/list corruption provides exploitable memory corruption primitives that can be leveraged for arbitrary kernel writes and privilege escalation.\nA:H - The vulnerability provokes kernel BUG/oops panics (demonstrated list_del corruption) and can be repeatedly triggered to crash or deny service via sustained carrier/watchdog races."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-17T05:45:12.038Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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        },
        {
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-74264",
    "datePublished": "2026-08-15T05:57:40.314Z",
    "dateReserved": "2026-08-15T05:44:03.877Z",
    "dateUpdated": "2026-08-17T05:45:12.038Z",
    "state": "PUBLISHED"
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      "date": "2026-09-05",
      "epss": "0.00162",
      "percentile": "0.05646"
    },
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      "cve": "CVE-2026-74264",
      "id": "msrc_CVE-2026-74264",
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      "source": "Microsoft CSAF VEX",
      "status": "final",
      "title": "net: watchdog: fix refcount tracking races",
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      "version": "1"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-74264\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-08-15T06:22:25.670\",\"lastModified\":\"2026-08-17T06:19:19.960\",\"vulnStatus\":\"Received\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nnet: watchdog: fix refcount tracking races\\n\\nBlamed commit converted the untracked dev_hold()/dev_put() calls\\nin the watchdog code to use the tracked dev_hold_track()/dev_put_track()\\n(which were later renamed/interfaced to netdev_hold() and netdev_put()).\\n\\nBy introducing dev-\u003ewatchdog_dev_tracker to store the\\nreference tracking information without adding synchronization\\nbetween netdev_watchdog_up() and dev_watchdog(), it enabled the\\nrace condition where this pointer could be overwritten or freed\\nconcurrently, leading to the list corruption crash syzbot reported:\\n\\nlist_del corruption, ffff888114a18c00-\u003enext is NULL\\n kernel BUG at lib/list_debug.c:52 !\\nOops: invalid opcode: 0000 [#1] SMP KASAN PTI\\nCPU: 1 UID: 0 PID: 91 Comm: kworker/u8:5 Not tainted syzkaller #0 PREEMPT(lazy)\\nHardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026\\nWorkqueue: events_unbound linkwatch_event\\n RIP: 0010:__list_del_entry_valid_or_report.cold+0x22/0x2a lib/list_debug.c:52\\nCall Trace:\\n \u003cTASK\u003e\\n  __list_del_entry_valid include/linux/list.h:132 [inline]\\n  __list_del_entry include/linux/list.h:246 [inline]\\n  list_move_tail include/linux/list.h:341 [inline]\\n  ref_tracker_free+0x1a7/0x6c0 lib/ref_tracker.c:329\\n  netdev_tracker_free include/linux/netdevice.h:4491 [inline]\\n  netdev_put include/linux/netdevice.h:4508 [inline]\\n  netdev_put include/linux/netdevice.h:4504 [inline]\\n  netdev_watchdog_down net/sched/sch_generic.c:600 [inline]\\n  dev_deactivate_many+0x28c/0xfe0 net/sched/sch_generic.c:1363\\n  dev_deactivate+0x109/0x1d0 net/sched/sch_generic.c:1397\\n  linkwatch_do_dev net/core/link_watch.c:184 [inline]\\n  linkwatch_do_dev+0xd3/0x120 net/core/link_watch.c:166\\n  __linkwatch_run_queue+0x3a5/0x810 net/core/link_watch.c:240\\n  linkwatch_event+0x8f/0xc0 net/core/link_watch.c:314\\n  process_one_work+0xa0e/0x1980 kernel/workqueue.c:3314\\n  process_scheduled_works kernel/workqueue.c:3397 [inline]\\n  worker_thread+0x5ef/0xe50 kernel/workqueue.c:3478\\n  kthread+0x370/0x450 kernel/kthread.c:436\\n  ret_from_fork+0x69a/0xc80 arch/x86/kernel/process.c:158\\n  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245\\n\\nThis patch has three coordinated parts:\\n\\n1) Add dev-\u003ewatchdog_lock and dev-\u003ewatchdog_ref_held to serialize watchdog operations.\\n\\n2) Remove netdev_watchdog_up() call from netif_carrier_on():\\n   This ensures netdev_watchdog_up() is only called from process/BH context\\n   (via linkwatch workqueue dev_activate()), allowing us to use\\n   spin_lock_bh() for synchronization.\\n\\n3) Synchronize watchdog up and watchdog timer:\\n   Protect netdev_watchdog_up() with tx_global_lock and watchdog_lock.\\n   Only allocate a new tracker in netdev_watchdog_up() if one is\\n   not already present.\\n   In dev_watchdog(), ensure we don\u0027t release the tracker if the\\n   timer was rescheduled either by dev_watchdog() itself or concurrently\\n   by netdev_watchdog_up().\"}],\"affected\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"affectedData\":[{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"unaffected\",\"programFiles\":[\"include/linux/netdevice.h\",\"net/core/dev.c\",\"net/sched/sch_generic.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"f12bf6f3f942b37de65eeea8be25903587fec930\",\"lessThan\":\"446fe8ce699ce0a4d702f7b0fcdb50de340b9260\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"f12bf6f3f942b37de65eeea8be25903587fec930\",\"lessThan\":\"7ce2b00ff058ec4cafc9b447e1f0a6d6f49275d9\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"f12bf6f3f942b37de65eeea8be25903587fec930\",\"lessThan\":\"8eed5519e496b7a07f441a0f579cb228a33189f7\",\"versionType\":\"git\",\"status\":\"affected\"}]},{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"affected\",\"programFiles\":[\"include/linux/netdevice.h\",\"net/core/dev.c\",\"net/sched/sch_generic.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"5.17\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"5.17\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.18.40\",\"lessThanOrEqual\":\"6.18.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.1.5\",\"lessThanOrEqual\":\"7.1.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.2\",\"lessThanOrEqual\":\"*\",\"versionType\":\"original_commit_for_fix\",\"status\":\"unaffected\"}]}]}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"type\":\"Secondary\",\"cvssData\":{\"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\",\"attackVector\":\"LOCAL\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"LOW\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":1.8,\"impactScore\":5.9}]},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/446fe8ce699ce0a4d702f7b0fcdb50de340b9260\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/7ce2b00ff058ec4cafc9b447e1f0a6d6f49275d9\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/8eed5519e496b7a07f441a0f579cb228a33189f7\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}",
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-09-01T10:37:51+00:00",
      "cve": "CVE-2026-74264",
      "id": "CVE-2026-74264",
      "initial_release_date": "2026-08-15T00:00:00+00:00",
      "product_status:known_affected": "198",
      "product_status:known_not_affected": "76",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: net: watchdog: fix refcount tracking races",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-74264.json",
      "version": "3"
    }
  }
}



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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.
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