{"id":"CVE-2026-43167","state":"PUBLISHED","title":"xfrm: always flush state and policy upon NETDEV_UNREGISTER event","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.","publishedAt":"2026-05-06T11:27:43.904Z","updatedAt":"2026-10-30T12:25:05.944Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"d77e38e612a017480157fe6d2c1422f42cb5b7e3","status":"affected","lessThan":"d4df5a7da376e35089b8b601a86ff8a4cf997e2f","versionType":"git"},{"version":"d77e38e612a017480157fe6d2c1422f42cb5b7e3","status":"affected","lessThan":"166801e49a5b5fc127b8c9e2f110f303cfddfbc3","versionType":"git"},{"version":"d77e38e612a017480157fe6d2c1422f42cb5b7e3","status":"affected","lessThan":"a3c8fede034fa27892f87c863cbd5493167d17ed","versionType":"git"},{"version":"d77e38e612a017480157fe6d2c1422f42cb5b7e3","status":"affected","lessThan":"59581778792cbaf8ad788f4a21dc663ce986050e","versionType":"git"},{"version":"d77e38e612a017480157fe6d2c1422f42cb5b7e3","status":"affected","lessThan":"8c75c455ecd3bfd2f36abf66edb7021c4fa19ec4","versionType":"git"},{"version":"d77e38e612a017480157fe6d2c1422f42cb5b7e3","status":"affected","lessThan":"4efa91a28576054aae0e6dad9cba8fed8293aef8","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/xfrm/xfrm_device.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"4.12","status":"affected"},{"version":"0","status":"unaffected","lessThan":"4.12","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.128","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.75","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.16","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19.6","status":"unaffected","lessThanOrEqual":"6.19.*","versionType":"semver"},{"version":"7.0","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/xfrm/xfrm_device.c"]}],"references":["https://git.kernel.org/stable/c/d4df5a7da376e35089b8b601a86ff8a4cf997e2f","https://git.kernel.org/stable/c/166801e49a5b5fc127b8c9e2f110f303cfddfbc3","https://git.kernel.org/stable/c/a3c8fede034fa27892f87c863cbd5493167d17ed","https://git.kernel.org/stable/c/59581778792cbaf8ad788f4a21dc663ce986050e","https://git.kernel.org/stable/c/8c75c455ecd3bfd2f36abf66edb7021c4fa19ec4","https://git.kernel.org/stable/c/4efa91a28576054aae0e6dad9cba8fed8293aef8"],"weaknesses":[],"ingestedAt":"2026-10-30T12:42:04.495Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/43xxx/CVE-2026-43167.json","commit":"db8103c5921aac81d5d90efcf3745980dafabf49","baselineCommit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-43167","state":"PUBLISHED","datePublished":"2026-05-06T11:27:43.904Z","dateUpdated":"2026-10-30T12:25:05.944Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-05-01T14:12:55.990Z"},"containers":{"cna":{"title":"xfrm: always flush state and policy upon NETDEV_UNREGISTER event","descriptions":[{"lang":"en","value":"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."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"d77e38e612a017480157fe6d2c1422f42cb5b7e3","status":"affected","lessThan":"d4df5a7da376e35089b8b601a86ff8a4cf997e2f","versionType":"git"},{"version":"d77e38e612a017480157fe6d2c1422f42cb5b7e3","status":"affected","lessThan":"166801e49a5b5fc127b8c9e2f110f303cfddfbc3","versionType":"git"},{"version":"d77e38e612a017480157fe6d2c1422f42cb5b7e3","status":"affected","lessThan":"a3c8fede034fa27892f87c863cbd5493167d17ed","versionType":"git"},{"version":"d77e38e612a017480157fe6d2c1422f42cb5b7e3","status":"affected","lessThan":"59581778792cbaf8ad788f4a21dc663ce986050e","versionType":"git"},{"version":"d77e38e612a017480157fe6d2c1422f42cb5b7e3","status":"affected","lessThan":"8c75c455ecd3bfd2f36abf66edb7021c4fa19ec4","versionType":"git"},{"version":"d77e38e612a017480157fe6d2c1422f42cb5b7e3","status":"affected","lessThan":"4efa91a28576054aae0e6dad9cba8fed8293aef8","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/xfrm/xfrm_device.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"4.12","status":"affected"},{"version":"0","status":"unaffected","lessThan":"4.12","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.128","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.75","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.16","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19.6","status":"unaffected","lessThanOrEqual":"6.19.*","versionType":"semver"},{"version":"7.0","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/xfrm/xfrm_device.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/d4df5a7da376e35089b8b601a86ff8a4cf997e2f"},{"url":"https://git.kernel.org/stable/c/166801e49a5b5fc127b8c9e2f110f303cfddfbc3"},{"url":"https://git.kernel.org/stable/c/a3c8fede034fa27892f87c863cbd5493167d17ed"},{"url":"https://git.kernel.org/stable/c/59581778792cbaf8ad788f4a21dc663ce986050e"},{"url":"https://git.kernel.org/stable/c/8c75c455ecd3bfd2f36abf66edb7021c4fa19ec4"},{"url":"https://git.kernel.org/stable/c/4efa91a28576054aae0e6dad9cba8fed8293aef8"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-30T12:25:05.944Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.12","versionEndExcluding":"6.1.191"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.12","versionEndExcluding":"6.6.128"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.12","versionEndExcluding":"6.12.75"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.12","versionEndExcluding":"6.18.16"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.12","versionEndExcluding":"6.19.6"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.12","versionEndExcluding":"7.0"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}