# CVE-2026-74264: net: watchdog: fix refcount tracking races CVE-2026-74264 is fixed in 20 products on 1 platform, first by DEBIAN-CVE-2026-74264, released August 15, 2026. It is not reported as exploited. Patch Radar priority: High. - Web page: https://patchblox.com/security/cve/CVE-2026-74264 - Priority: High - CVSS: 7.8 (Moderate) - EPSS: 0.0018 - CISA KEV: not listed - Exploited (vendor report): no - Publicly disclosed: no - Published: Aug 15, 2026 - Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-74264 ## Description 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: __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(). ## Where it's fixed | Platform | Product | Fixed in | Fix | Released | |---|---|---|---|---| | Linux | bpftool6.18 amzn 2023 | 1:6.18.41-94.142.amzn2023 | [ALAS2023-2026-2071](https://patchblox.com/security/data/fix/linux/alas2023-2026-2071.md) | Aug 31, 2026 | | Linux | bpftool6.18-debuginfo amzn 2023 | 1:6.18.41-94.142.amzn2023 | [ALAS2023-2026-2071](https://patchblox.com/security/data/fix/linux/alas2023-2026-2071.md) | Aug 31, 2026 | | Linux | kernel-livepatch-6.18.41-94.142 amzn 2023 | 1:1.0-0.amzn2023 | [ALAS2023-2026-2071](https://patchblox.com/security/data/fix/linux/alas2023-2026-2071.md) | Aug 31, 2026 | | Linux | kernel6.18 amzn 2023 | 1:6.18.41-94.142.amzn2023 | [ALAS2023-2026-2071](https://patchblox.com/security/data/fix/linux/alas2023-2026-2071.md) | Aug 31, 2026 | | Linux | kernel6.18-debuginfo amzn 2023 | 1:6.18.41-94.142.amzn2023 | [ALAS2023-2026-2071](https://patchblox.com/security/data/fix/linux/alas2023-2026-2071.md) | Aug 31, 2026 | | Linux | kernel6.18-debuginfo-common-aarch64 amzn 2023 | 1:6.18.41-94.142.amzn2023 | [ALAS2023-2026-2071](https://patchblox.com/security/data/fix/linux/alas2023-2026-2071.md) | Aug 31, 2026 | | Linux | kernel6.18-debuginfo-common-x86_64 amzn 2023 | 1:6.18.41-94.142.amzn2023 | [ALAS2023-2026-2071](https://patchblox.com/security/data/fix/linux/alas2023-2026-2071.md) | Aug 31, 2026 | | Linux | kernel6.18-devel amzn 2023 | 1:6.18.41-94.142.amzn2023 | [ALAS2023-2026-2071](https://patchblox.com/security/data/fix/linux/alas2023-2026-2071.md) | Aug 31, 2026 | | Linux | kernel6.18-headers amzn 2023 | 1:6.18.41-94.142.amzn2023 | [ALAS2023-2026-2071](https://patchblox.com/security/data/fix/linux/alas2023-2026-2071.md) | Aug 31, 2026 | | Linux | kernel6.18-modules-extra amzn 2023 | 1:6.18.41-94.142.amzn2023 | [ALAS2023-2026-2071](https://patchblox.com/security/data/fix/linux/alas2023-2026-2071.md) | Aug 31, 2026 | | Linux | kernel6.18-modules-extra-common amzn 2023 | 1:6.18.41-94.142.amzn2023 | [ALAS2023-2026-2071](https://patchblox.com/security/data/fix/linux/alas2023-2026-2071.md) | Aug 31, 2026 | | Linux | kernel6.18-tools amzn 2023 | 1:6.18.41-94.142.amzn2023 | [ALAS2023-2026-2071](https://patchblox.com/security/data/fix/linux/alas2023-2026-2071.md) | Aug 31, 2026 | | Linux | kernel6.18-tools-debuginfo amzn 2023 | 1:6.18.41-94.142.amzn2023 | [ALAS2023-2026-2071](https://patchblox.com/security/data/fix/linux/alas2023-2026-2071.md) | Aug 31, 2026 | | Linux | kernel6.18-tools-devel amzn 2023 | 1:6.18.41-94.142.amzn2023 | [ALAS2023-2026-2071](https://patchblox.com/security/data/fix/linux/alas2023-2026-2071.md) | Aug 31, 2026 | | Linux | linux Debian 13.5 (trixie) | 6.12.115-2 | [DEBIAN-CVE-2026-74264](https://patchblox.com/security/data/fix/linux/debian-cve-2026-74264.md) | Aug 15, 2026 | | Linux | linux Debian 14 | 7.1.5-1 | [DEBIAN-CVE-2026-74264](https://patchblox.com/security/data/fix/linux/debian-cve-2026-74264.md) | Aug 15, 2026 | | Linux | microvm-kernel6.18 amzn 2023 | 1:6.18.41-94.142.amzn2023 | [ALAS2023-2026-2071](https://patchblox.com/security/data/fix/linux/alas2023-2026-2071.md) | Aug 31, 2026 | | Linux | perf6.18 amzn 2023 | 1:6.18.41-94.142.amzn2023 | [ALAS2023-2026-2071](https://patchblox.com/security/data/fix/linux/alas2023-2026-2071.md) | Aug 31, 2026 | | Linux | perf6.18-debuginfo amzn 2023 | 1:6.18.41-94.142.amzn2023 | [ALAS2023-2026-2071](https://patchblox.com/security/data/fix/linux/alas2023-2026-2071.md) | Aug 31, 2026 | | Linux | python3-perf6.18 amzn 2023 | 1:6.18.41-94.142.amzn2023 | [ALAS2023-2026-2071](https://patchblox.com/security/data/fix/linux/alas2023-2026-2071.md) | Aug 31, 2026 | | Linux | python3-perf6.18-debuginfo amzn 2023 | 1:6.18.41-94.142.amzn2023 | [ALAS2023-2026-2071](https://patchblox.com/security/data/fix/linux/alas2023-2026-2071.md) | Aug 31, 2026 | --- Data as of 2026-11-08T06:59:42Z UTC. 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