CVE Catalog

CVE-2026-19939

MediumCVSS 6.3
Published: Updated: Translated: NVD NIST

Exploitation Probability (EPSS)

Low risk
0.18%

7th percentile - higher than 7% of all known CVEs

Summary

In the AVDTP signalling layer of the Zephyr RTOS Bluetooth stack, the L2CAP disconnect handler (bt_avdtp_l2cap_disconnected) failed to cancel the armed delayed timeout_work, leaving it linked in the kernel's global timeout list. When the bt_avdtp session struct is zeroed by memset() on reconnect, the kernel treats the still-linked timeout node as free, corrupting the global timeout list and causing a system-wide crash or hang. The vulnerability requires CONFIG_BT_A2DP (experimental) to be enabled and an encrypted BR/EDR link.

Risk Assessment

A remote attacker within Bluetooth range can trigger a crash or hang of the entire system (denial of service), not just the A2DP session, because a core kernel data structure used by all timers and scheduling is corrupted. It requires an encrypted BR/EDR link and the experimental A2DP support to be enabled.

Recommendation

Update to a version containing the fix that cancels session->timeout_work at the top of bt_avdtp_l2cap_disconnected() and moves k_work_init_delayable() into the session-establishment paths (bt_avdtp_connect() and bt_avdtp_l2cap_accept()). If updating is not possible, consider disabling CONFIG_BT_A2DP until the fix is deployed.

Related vulnerabilities

Original NVD description (English source)

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.

Vulnerability data from NVD (NIST) · CISA KEV · EPSS