{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-23192", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-01-13T15:37:45.985Z", "datePublished": "2026-02-14T16:27:19.557Z", "dateUpdated": "2026-08-05T12:20:34.811Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T12:20:34.811Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nlinkwatch: use __dev_put() in callers to prevent UAF\n\nAfter linkwatch_do_dev() calls __dev_put() to release the linkwatch\nreference, the device refcount may drop to 1. At this point,\nnetdev_run_todo() can proceed (since linkwatch_sync_dev() sees an\nempty list and returns without blocking), wait for the refcount to\nbecome 1 via netdev_wait_allrefs_any(), and then free the device\nvia kobject_put().\n\nThis creates a use-after-free when __linkwatch_run_queue() tries to\ncall netdev_unlock_ops() on the already-freed device.\n\nNote that adding netdev_lock_ops()/netdev_unlock_ops() pair in\nnetdev_run_todo() before kobject_put() would not work, because\nnetdev_lock_ops() is conditional - it only locks when\nnetdev_need_ops_lock() returns true. If the device doesn't require\nops_lock, linkwatch won't hold any lock, and netdev_run_todo()\nacquiring the lock won't provide synchronization.\n\nFix this by moving __dev_put() from linkwatch_do_dev() to its\ncallers. The device reference logically pairs with de-listing the\ndevice, so it's reasonable for the caller that did the de-listing\nto release it. This allows placing __dev_put() after all device\naccesses are complete, preventing UAF.\n\nThe bug can be reproduced by adding mdelay(2000) after\nlinkwatch_do_dev() in __linkwatch_run_queue(), then running:\n\n ip tuntap add mode tun name tun_test\n ip link set tun_test up\n ip link set tun_test carrier off\n ip link set tun_test carrier on\n sleep 0.5\n ip tuntap del mode tun name tun_test\n\nKASAN report:\n\n ==================================================================\n BUG: KASAN: use-after-free in netdev_need_ops_lock include/net/netdev_lock.h:33 [inline]\n BUG: KASAN: use-after-free in netdev_unlock_ops include/net/netdev_lock.h:47 [inline]\n BUG: KASAN: use-after-free in __linkwatch_run_queue+0x865/0x8a0 net/core/link_watch.c:245\n Read of size 8 at addr ffff88804de5c008 by task kworker/u32:10/8123\n\n CPU: 0 UID: 0 PID: 8123 Comm: kworker/u32:10 Not tainted syzkaller #0 PREEMPT(full)\n Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014\n Workqueue: events_unbound linkwatch_event\n Call Trace:\n \n __dump_stack lib/dump_stack.c:94 [inline]\n dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120\n print_address_description mm/kasan/report.c:378 [inline]\n print_report+0x156/0x4c9 mm/kasan/report.c:482\n kasan_report+0xdf/0x1a0 mm/kasan/report.c:595\n netdev_need_ops_lock include/net/netdev_lock.h:33 [inline]\n netdev_unlock_ops include/net/netdev_lock.h:47 [inline]\n __linkwatch_run_queue+0x865/0x8a0 net/core/link_watch.c:245\n linkwatch_event+0x8f/0xc0 net/core/link_watch.c:304\n process_one_work+0x9c2/0x1840 kernel/workqueue.c:3257\n process_scheduled_works kernel/workqueue.c:3340 [inline]\n worker_thread+0x5da/0xe40 kernel/workqueue.c:3421\n kthread+0x3b3/0x730 kernel/kthread.c:463\n ret_from_fork+0x754/0xaf0 arch/x86/kernel/process.c:158\n ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246\n \n ==================================================================" } ], "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 vulnerability is triggered through local operations: creating a tun device, manipulating carrier state via netlink (RTM_SETLINK/IFLA_CARRIER), and deleting the device. All require local system access via syscalls/netlink.\nAC:L - The attacker controls both sides of the race - they fire the linkwatch event by changing carrier state AND initiate device deletion. The reproducer shows reliable triggering with a simple sleep. The attacker creates and controls the race condition.\nPR:L - Creating tun devices and manipulating carrier state requires CAP_NET_ADMIN, but this capability is available in user namespaces via unshare -Urn (ns_capable check in tun.c:2757), making this reachable by unprivileged local users.\nUI:N - No user interaction is needed. The attacker autonomously creates the device, manipulates carrier state, and triggers the race to cause the UAF.\nS:U - The vulnerability results in kernel memory corruption within the same security authority (the kernel). There is no crossing of a virtualization or sandbox boundary.\nC:H - This is a use-after-free on a net_device structure. The freed memory can be reclaimed and filled with attacker-controlled data via heap spraying, enabling arbitrary kernel memory reads through the stale pointer.\nI:H - The UAF on the net_device structure allows heap spraying to place attacker-controlled data in the freed allocation. This enables write primitives and potential control flow hijacking through the stale device pointer operations.\nA:H - The UAF reliably causes a kernel crash/oops as demonstrated by the KASAN report. Accessing freed memory in netdev_unlock_ops triggers an immediate kernel crash." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/core/link_watch.c" ], "versions": [ { "version": "04efcee6ef8d0f01eef495db047e7216d6e6e38f", "lessThan": "2718ae6af7445ba2ee0abf6365ca43a9a3b16aeb", "status": "affected", "versionType": "git" }, { "version": "04efcee6ef8d0f01eef495db047e7216d6e6e38f", "lessThan": "83b67cc9be9223183caf91826d9c194d7fb128fa", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/core/link_watch.c" ], "versions": [ { "version": "6.15", "status": "affected" }, { "version": "0", "lessThan": "6.15", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.10", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.19", "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": "6.15", "versionEndExcluding": "6.18.10" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.15", "versionEndExcluding": "6.19" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/2718ae6af7445ba2ee0abf6365ca43a9a3b16aeb" }, { "url": "https://git.kernel.org/stable/c/83b67cc9be9223183caf91826d9c194d7fb128fa" } ], "title": "linkwatch: use __dev_put() in callers to prevent UAF", "x_generator": { "engine": "bippy-1.2.0" } } } }