CVE-2026-97975
UnknownSummary
A race condition exists in the Linux kernel between hci_conn_del_sysfs() and concurrent unregistration of a child device (e.g., a BNEP network device in bnep_session). During unregistration, device_del() uses a stale parent pointer, leading to a NULL pointer dereference in klist_put(). The issue is fixed by holding an explicit reference to the parent device (get_device/put_device) and restoring the __match_tty filter.
Risk Assessment
The vulnerability can cause a kernel panic and denial of service (DoS) on systems with active Bluetooth, especially when BNEP network devices are being disconnected concurrently. However, it requires specific race conditions, limiting exploitability.
Recommendation
Update the Linux kernel to a version containing the fix (the commit addressing this issue). If immediate update is not possible, consider minimizing Bluetooth/BNEP usage to essential needs.
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Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: Bluetooth: hci_sysfs: Fix NULL pointer dereference in device_del() A NULL pointer dereference in klist_put() occurs when a child device (such as a BNEP network device in bnep_session) is concurrently being unregistered while hci_conn_del_sysfs() reparents child devices. This is caused by a race condition between hci_conn_del_sysfs() and concurrent child device unregistration (e.g. bnep_session calling unregister_netdev()). During device unregistration, device_del() snapshots a non-NULL parent pointer. Concurrently, hci_conn_del_sysfs() finds the child device using device_find_any_child() and calls device_move() to reparent it to NULL, which removes the node from its parent's klist and clears knode_parent. Subsequently, device_del() calls klist_del(&dev->p->knode_parent) using the stale parent snapshot, causing klist_put() to dereference knode_klist(n)->put on an already removed node, resulting in a NULL pointer dereference. This race was introduced by commit 27aabf27fd01 ("Bluetooth: fix use-after-free in device_for_each_child()"), which replaced device_find_child(..., __match_tty) with device_find_any_child() in hci_conn_del_sysfs(). That change was intended to avoid a use-after-free where conn->dev outlived its parent hdev->dev when child devices held references to conn->dev, because conn->dev only held a reference to hdev->dev while registered in sysfs. Fix the issue properly by taking an explicit reference to the parent device with get_device(&hdev->dev) in hci_conn_init_sysfs() and dropping it with put_device(parent) in bt_link_release() when the conn device is freed. This ensures that hdev->dev remains valid for the entire lifecycle of conn->dev, resolving the underlying use-after-free. With the parent reference held properly, restore the __match_tty filter in hci_conn_del_sysfs() so that device_move() is only invoked on persistent RFCOMM TTY devices as originally intended, eliminating the race condition with unregistering network devices.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS