The AVDTP signalling layer arms a 6-second command timeout (AVDTP_TIMEOUT) in avdtp_send_cmd() whenever the local device issues an AVDTP request. Every response handler in subsys/bluetooth/host/classic/avdtp.c cancels session->timeout_work before clearing the pending request, but bt_avdtp_l2cap_disconnected() only cleared session->req and left the delayable work armed. The struct bt_avdtp session is the first member of struct bt_a2dp, whose instances live in a static per-connection array, and a2dp_get_connection() in subsys/bluetooth/host/classic/a2dp.c wipes a slot with memset() as soon as session->br_chan.chan.conn is NULL — which the L2CAP layer arranges immediately after the disconnect callback returns. A remote Bluetooth BR/EDR peer triggers the condition by opening the AVDTP signalling channel, letting the local application issue an AVDTP procedure (the standard A2DP flow issues bt_a2dp_discover() from the connected callback), then tearing the signalling channel down without responding and re-opening it within the remaining timeout window. The reconnect reaches a2dp_accept() → a2dp_get_connection(), which zeroes the whole struct bt_a2dp while the work item's struct _timeout is still linked into the kernel's global timeout list. Both the disconnect and the reconnect instants are chosen by the attacker, so no race has to be won; an encrypted BR/EDR link is required, and CONFIG_BT_A2DP (experimental) must be enabled. With the default CONFIG_TIMEOUT_BACKEND_DLIST backend the kernel decides a timeout is inactive by testing whether its list node is linked, so after the memset() the kernel treats a node that is still on the global timeout list as free: the announce path pops a node whose links and handler pointer are NULL, and the next bt_work_reschedule() on the recycled session re-inserts the same node into a list that already contains it. The consequence is corruption of the single kernel data structure every timer, timeslice and sleep depends on — writes through zeroed or stale list pointers and a NULL handler dispatch — producing a system-wide crash or hang rather than a fault confined to the A2DP session. The fix cancels session->timeout_work at the top of bt_avdtp_l2cap_disconnected() and moves k_work_init_delayable() from avdtp_send_cmd() to the session-establishment paths bt_avdtp_connect() and bt_avdtp_l2cap_accept(), so the work item is always initialized before a disconnect callback can run.
| Métrique | Valeur | Interprétation |
|---|---|---|
|
AV (Vecteur d'Attaque)
Attack Vector
|
Adjacent (A)
|
Exploit nécessite un accès au segment réseau local |
|
AC (Complexité d'Attaque)
Attack Complexity
|
Low (L)
|
Peu de conditions requises pour exploiter |
|
PR (Privilèges Requis)
Privileges Required
|
Low (L)
|
Authentifié avec compte utilisateur basique |
|
UI (Interaction Utilisateur)
User Interaction
|
None (N)
|
Aucune interaction utilisateur nécessaire |
|
S (Périmètre)
Scope
|
Unchanged (U)
|
Impact reste dans le périmètre du composant compromis |
|
C (Impact Confidentialité)
Confidentiality Impact
|
None (N)
|
Aucune divulgation d'informations |
|
I (Impact Intégrité)
Integrity Impact
|
Low (L)
|
Modification limitée des données possible |
|
A (Impact Disponibilité)
Availability Impact
|
High (H)
|
Interruption totale du service possible |
Bluetooth Classic AVDTP: stale timeout work on signalling-channel disconnect leads to kernel timeout-list corruption