{"id":"CVE-2026-19940","summary":"Bluetooth HFP AG reuses a connection slot while a delayable work item is still armed, corrupting kernel timeout bookkeeping","details":"The Bluetooth Classic Hands-Free Profile Audio Gateway implementation in subsys/bluetooth/host/classic/hfp_ag.c keeps its struct bt_hfp_ag objects in a static pool indexed by ACL connection index. On link teardown, hfp_ag_disconnected() cancels ag-\u003etx_work and the per-call work items and then clears ag-\u003eacl_conn, which marks the pool slot as free — but it leaves ag-\u003eongoing_call_work (and ag-\u003eslc_work) untouched. The next connection that lands on the same slot enters hfp_ag_create(), whose only occupancy test is ag-\u003eacl_conn, and immediately executes memset(ag, 0, sizeof(struct bt_hfp_ag)) followed by k_work_init_delayable(). Zeroing and re-initialising a k_work_delayable whose struct _timeout node is still linked into the kernel timeout list leaves the kernel holding a reference to a node with NULL prev/next links.\n\nag-\u003eongoing_call_work is armed by the remote peer: when a Hands-Free unit sends AT+CIND? during Service Level Connection establishment and the application provides the asynchronous get_ongoing_call callback, the AG schedules the work for CONFIG_BT_HFP_AG_GET_ONGOING_CALL_TIMEOUT milliseconds (default 10000). The timer is cancelled only if the application answers in time via bt_hfp_ag_ongoing_calls(). A peer that sends AT+CIND?, then disconnects the HFP RFCOMM DLC, then immediately re-opens it on the same ACL link, reuses the same pool slot deterministically while the timeout is still pending — the AG's RFCOMM server accept path (hfp_ag_accept()) calls hfp_ag_create() directly, so the remote side drives both teardown and re-creation.\n\nThe result is corruption of the kernel's timeout list: sys_dlist_remove() on the zeroed node performs writes through NULL pointers from the clock-announce path, and rescheduling the re-initialised work re-inserts a node the list already references, creating a cycle that the announce loop walks with interrupts locked. The observable impact is a fault or hang of the whole system, i.e. a denial of service reachable from Bluetooth radio range; no attacker-controlled data is written, so this does not by itself yield code execution. Exposure is limited to builds with CONFIG_BT_HFP_AG (marked experimental and disabled by default) whose application implements the asynchronous get_ongoing_call callback.","aliases":["GHSA-v47w-8959-rx62"],"modified":"2026-10-15T10:47:31.318073625Z","published":"2026-10-13T16:40:10.541Z","database_specific":{"cna_assigner":"zephyr","cwe_ids":["CWE-416"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/19xxx/CVE-2026-19940.json"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/19xxx/CVE-2026-19940.json"},{"type":"ADVISORY","url":"https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-v47w-8959-rx62"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-19940"},{"type":"FIX","url":"https://github.com/zephyrproject-rtos/zephyr/commit/204c36b896fe8d68ca3cb3d00216f245f91d14be"},{"type":"PACKAGE","url":"https://github.com/zephyrproject-rtos/zephyr"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/zephyrproject-rtos/zephyr","events":[{"introduced":"413b789deb391d3a37d06b463288a5fe765ee57e"},{"fixed":"204c36b896fe8d68ca3cb3d00216f245f91d14be"}],"database_specific":{"source":["AFFECTED_FIELD","REFERENCES"],"extracted_events":[{"introduced":"4.2.0"},{"last_affected":"4.4.2"}]}}],"versions":["v4.4.0","v4.4.0-rc3","v4.4.0-rc2","v4.4.0-rc1","v4.3.0","v4.3.0-rc3","v4.3.0-rc2","v4.3.0-rc1","v4.2.0"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-19940.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"}]}