{"schema":"threatline.record/2","record":{"id":"CVE-2026-19939","aliases":["GHSA-9mww-f3h4-mq95"],"summary":"Bluetooth Classic AVDTP: stale timeout work on signalling-channel disconnect leads to kernel timeout-list corruption","details":"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.\n\nA 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.\n\nWith 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.\n\nThe 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.","categories":["Unclassified"],"product":"zephyr","vendor":"zephyrproject","ecosystem":null,"affected_ranges":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-19939","source_modified_at":"2026-10-14T18:49:17.902Z","fetched_at":"2026-10-23T18:48:36.087640Z","product":"zephyr","vendor":"zephyrproject","versions":[{"version":"3.7.0","status":"affected","versionType":"semver","lessThanOrEqual":"4.4.2"}],"defaultStatus":"unaffected"}],"fixed_versions":[],"cvss":6.3,"severity":"Medium","kev":{"listed":false},"epss":{"probability":0.00179,"percentile":0.07088,"score_date":"2026-10-23"},"published_at":"2026-10-13T16:39:16.681Z","modified_at":"2026-10-14T18:49:17.902Z","provenance":[{"source":"CVE List","url":"https://www.cve.org/CVERecord?id=CVE-2026-19939","fetched_at":"2026-10-23T18:48:36.087640Z","source_modified_at":"2026-10-14T18:49:17.902Z"},{"source":"EPSS","url":"https://api.first.org/data/v1/epss?cve=CVE-2026-19939","fetched_at":"2026-10-23T18:42:43.628194Z","source_modified_at":"2026-10-23"}],"sources":["CVE List","EPSS"],"references":[{"source":"CVE List","url":"https://github.com/zephyrproject-rtos/zephyr/commit/a10d18c3be9d1a968574dbfbce6baee58ea398e8","tags":["patch"]},{"source":"CVE List","url":"https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-9mww-f3h4-mq95"}],"locations":[],"motoko_assessment":{"status":"requires_architecture_review","automatic_remediation":false},"cve_state":"PUBLISHED","cvss_source":"CVE List","ssvc":{"exploitation":"none","automatable":"no","technical_impact":"partial","assessed_at":"2026-10-14T18:49:00.544306Z"},"classification":{"method":"product-first software-layer rules","rules_version":"2.1","matched_on":null,"confidence":"unknown","reviewed":false},"change_timestamp":"2026-10-14T18:49:17.902Z","content_hash":"9c1868ea94d0c2eb829618db1d4b0f7652a44c56ecceacd167e800572633d13e"}}