{"id":"CVE-2026-43167","url":"https://www.cyber-defence.io/tools/cve/CVE-2026-43167","generatedAt":"2026-10-28T05:46:21.780Z","title":"In the Linux kernel, the following vulnerability has been resolved: xfrm: always flush state and policy upon NETDEV_UNREGISTER event syzbot is reporting that \"struct xfrm_state\" refcount is leaking. unregister_netdevice: waiting for netdevsim0 to become…","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nxfrm: always flush state and policy upon NETDEV_UNREGISTER event\n\nsyzbot is reporting that \"struct xfrm_state\" refcount is leaking.\n\n  unregister_netdevice: waiting for netdevsim0 to become free. Usage count = 2\n  ref_tracker: netdev@ffff888052f24618 has 1/1 users at\n       __netdev_tracker_alloc include/linux/netdevice.h:4400 [inline]\n       netdev_tracker_alloc include/linux/netdevice.h:4412 [inline]\n       xfrm_dev_state_add+0x3a5/0x1080 net/xfrm/xfrm_device.c:316\n       xfrm_state_construct net/xfrm/xfrm_user.c:986 [inline]\n       xfrm_add_sa+0x34ff/0x5fa0 net/xfrm/xfrm_user.c:1022\n       xfrm_user_rcv_msg+0x58e/0xc00 net/xfrm/xfrm_user.c:3507\n       netlink_rcv_skb+0x158/0x420 net/netlink/af_netlink.c:2550\n       xfrm_netlink_rcv+0x71/0x90 net/xfrm/xfrm_user.c:3529\n       netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]\n       netlink_unicast+0x5aa/0x870 net/netlink/af_netlink.c:1344\n       netlink_sendmsg+0x8c8/0xdd0 net/netlink/af_netlink.c:1894\n       sock_sendmsg_nosec net/socket.c:727 [inline]\n       __sock_sendmsg net/socket.c:742 [inline]\n       ____sys_sendmsg+0xa5d/0xc30 net/socket.c:2592\n       ___sys_sendmsg+0x134/0x1d0 net/socket.c:2646\n       __sys_sendmsg+0x16d/0x220 net/socket.c:2678\n       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]\n       do_syscall_64+0xcd/0xf80 arch/x86/entry/syscall_64.c:94\n       entry_SYSCALL_64_after_hwframe+0x77/0x7f\n\nThis is because commit d77e38e612a0 (\"xfrm: Add an IPsec hardware\noffloading API\") implemented xfrm_dev_unregister() as no-op despite\nxfrm_dev_state_add() from xfrm_state_construct() acquires a reference\nto \"struct net_device\".\nI guess that that commit expected that NETDEV_DOWN event is fired before\nNETDEV_UNREGISTER event fires, and also assumed that xfrm_dev_state_add()\nis called only if (dev->features & NETIF_F_HW_ESP) != 0.\n\nSabrina Dubroca identified steps to reproduce the same symptoms as below.\n\n  echo 0 > /sys/bus/netdevsim/new_device\n  dev=$(ls -1 /sys/bus/netdevsim/devices/netdevsim0/net/)\n  ip xfrm state add src 192.168.13.1 dst 192.168.13.2 proto esp \\\n     spi 0x1000 mode tunnel aead 'rfc4106(gcm(aes))' $key 128   \\\n     offload crypto dev $dev dir out\n  ethtool -K $dev esp-hw-offload off\n  echo 0 > /sys/bus/netdevsim/del_device\n\nLike these steps indicate, the NETIF_F_HW_ESP bit can be cleared after\nxfrm_dev_state_add() acquired a reference to \"struct net_device\".\nAlso, xfrm_dev_state_add() does not check for the NETIF_F_HW_ESP bit\nwhen acquiring a reference to \"struct net_device\".\n\nCommit 03891f820c21 (\"xfrm: handle NETDEV_UNREGISTER for xfrm device\")\nre-introduced the NETDEV_UNREGISTER event to xfrm_dev_event(), but that\ncommit for unknown reason chose to share xfrm_dev_down() between the\nNETDEV_DOWN event and the NETDEV_UNREGISTER event.\nI guess that that commit missed the behavior in the previous paragraph.\n\nTherefore, we need to re-introduce xfrm_dev_unregister() in order to\nrelease the reference to \"struct net_device\" by unconditionally flushing\nstate and policy.","published":"2026-05-06T12:16:35.000Z","lastModified":"2026-06-17T10:49:04.000Z","status":"Analyzed","sourceIdentifier":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","cvss":{"version":"3.1","score":5.5,"severity":"MEDIUM","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H"},"cwe":[],"affected":["linux/linux kernel"],"epss":{"score":0.00122,"percentile":0.01966,"date":"2026-10-27","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"low","text":"Lower severity and a low EPSS score (0.12%). Track it; it rarely justifies an emergency change on its own."},"changes":[],"references":[{"url":"https://git.kernel.org/stable/c/166801e49a5b5fc127b8c9e2f110f303cfddfbc3","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/4efa91a28576054aae0e6dad9cba8fed8293aef8","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/59581778792cbaf8ad788f4a21dc663ce986050e","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/8c75c455ecd3bfd2f36abf66edb7021c4fa19ec4","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/a3c8fede034fa27892f87c863cbd5493167d17ed","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-43167","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}