{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-74264", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-08-15T05:44:03.877Z", "datePublished": "2026-08-15T05:57:40.314Z", "dateUpdated": "2026-08-17T05:45:12.038Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-17T05:45:12.038Z" }, "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->watchdog_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->next 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 \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->watchdog_lock and dev->watchdog_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't release the tracker if the\n timer was rescheduled either by dev_watchdog() itself or concurrently\n by netdev_watchdog_up()." } ], "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 - 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." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "include/linux/netdevice.h", "net/core/dev.c", "net/sched/sch_generic.c" ], "versions": [ { "version": "f12bf6f3f942b37de65eeea8be25903587fec930", "lessThan": "446fe8ce699ce0a4d702f7b0fcdb50de340b9260", "status": "affected", "versionType": "git" }, { "version": "f12bf6f3f942b37de65eeea8be25903587fec930", "lessThan": "7ce2b00ff058ec4cafc9b447e1f0a6d6f49275d9", "status": "affected", "versionType": "git" }, { "version": "f12bf6f3f942b37de65eeea8be25903587fec930", "lessThan": "8eed5519e496b7a07f441a0f579cb228a33189f7", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "include/linux/netdevice.h", "net/core/dev.c", "net/sched/sch_generic.c" ], "versions": [ { "version": "5.17", "status": "affected" }, { "version": "0", "lessThan": "5.17", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.40", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.1.5", "lessThanOrEqual": "7.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.17", "versionEndExcluding": "6.18.40" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.17", "versionEndExcluding": "7.1.5" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.17", "versionEndExcluding": "7.2" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/446fe8ce699ce0a4d702f7b0fcdb50de340b9260" }, { "url": "https://git.kernel.org/stable/c/7ce2b00ff058ec4cafc9b447e1f0a6d6f49275d9" }, { "url": "https://git.kernel.org/stable/c/8eed5519e496b7a07f441a0f579cb228a33189f7" } ], "title": "net: watchdog: fix refcount tracking races", "x_generator": { "engine": "bippy-1.2.0" } } } }