Linux Kernel up to 6.18.39/7.1.4 Watchdog net/sched/sch_generic.c netdev_watchdog_up watchdog_dev_tracker race condition

CVSS Meta Temp Score
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CTI Interest Score
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5.2$0-$5k0.47+

Summaryinfo

A vulnerability, which was classified as problematic, has been found in Linux Kernel up to 6.18.39/7.1.4. This impacts the function netdev_watchdog_up of the file net/sched/sch_generic.c of the component Watchdog. This manipulation of the argument watchdog_dev_tracker causes race condition. This vulnerability appears as CVE-2026-74264. The attack may be initiated remotely. There is no available exploit.

Detailsinfo

A vulnerability classified as problematic was found in Linux Kernel up to 6.18.39/7.1.4. Affected by this vulnerability is the function netdev_watchdog_up of the file net/sched/sch_generic.c of the component Watchdog. The manipulation of the argument watchdog_dev_tracker with an unknown input leads to a race condition vulnerability. The CWE definition for the vulnerability is CWE-362. The product contains a code sequence that can run concurrently with other code, and the code sequence requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence that is operating concurrently. As an impact it is known to affect integrity, and availability. The summary by CVE is:

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().

It is possible to read the advisory at git.kernel.org. This vulnerability is known as CVE-2026-74264 since 08/15/2026. The exploitation appears to be easy. The attack can be launched remotely. Technical details of the vulnerability are known, but there is no available exploit. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 08/15/2026).

Upgrading to version 6.18.40, 7.1.5 or 7.2-rc1 eliminates this vulnerability. Applying the patch 446fe8ce699ce0a4d702f7b0fcdb50de340b9260/7ce2b00ff058ec4cafc9b447e1f0a6d6f49275d9/8eed5519e496b7a07f441a0f579cb228a33189f7 is able to eliminate this problem.

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Productinfo

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Vendor

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Version

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CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 5.4
VulDB Meta Temp Score: 5.2

VulDB Base Score: 5.4
VulDB Temp Score: 5.2
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

AVACAuCIA
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💳💳💳💳💳💳
VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Race condition
CWE: CWE-362
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined
Price Prediction: 🔍
Current Price Estimation: 🔒

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Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Kernel 6.18.40/7.1.5/7.2-rc1
Patch: 446fe8ce699ce0a4d702f7b0fcdb50de340b9260/7ce2b00ff058ec4cafc9b447e1f0a6d6f49275d9/8eed5519e496b7a07f441a0f579cb228a33189f7

Timelineinfo

08/15/2026 Advisory disclosed
08/15/2026 +0 days CVE reserved
08/15/2026 +0 days VulDB entry created
08/15/2026 +0 days VulDB entry last update

Sourcesinfo

Vendor: kernel.org

Advisory: git.kernel.org
Status: Confirmed

CVE: CVE-2026-74264 (🔒)
GCVE (CVE): GCVE-0-2026-74264
GCVE (VulDB): GCVE-100-390223

Entryinfo

Created: 08/15/2026 08:38
Changes: 08/15/2026 08:38 (61)
Complete: 🔍
Cache ID: 216::103

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