CVE-2026-85033 Falta de limpieza de TX en AVRCP Target de Bluetooth Classic al desconectarse

Afectados

• zephyrproject zephyr

  desde 4.4.0 hasta antes de 4.5.0

Qué hacer

1. Verificá si usás zephyr y en qué versión.
2. Actualizá a la versión corregida que indique el fabricante en su aviso o aplicá su mitigación.
3. Revisá registros y accesos de los sistemas expuestos para descartar un uso previo.

Calculadora CVSS

CVSS 3.1 · 4.6 MEDIA

CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:L

• Vector de ataqueRed adyacente
• Complejidad del ataqueBaja
• Privilegios requeridosBajos
• Interacción del usuarioNinguna
• AlcanceSin cambio
• ConfidencialidadBaja
• IntegridadNinguna
• DisponibilidadBaja

Descripción original

The AVRCP Target role in subsys/bluetooth/host/classic/avrcp.c keeps its vendor-dependent response transmit state in a per-connection object selected by connection index (get_avrcp_tg()), with the per-transfer context (tid, sent_len, and the BT_AVRCP_TG_FLAG_TX_ONGOING flag) stored in the user_data of the queued response net_buf. The AVCTP teardown handler avrcp_disconnected() did not cancel tg->vd_rsp_tx_work and did not release the buffers still queued on tg->vd_rsp_tx_pending, so a link drop in the middle of a fragmented response left the buffer on the list with TX_ONGOING still set. A remote AVRCP Controller can trigger this deterministically: it issues a vendor-dependent command whose response exceeds one AVRCP fragment (for example GetElementAttributes or GetCapabilities), lets bt_avrcp_tg_vendor_tx_work() emit the START fragment, and then drops the ACL link instead of sending REQUEST_CONTINUING_RESPONSE. The AVCTP control channel requires an encrypted BR/EDR link (BT_SECURITY_L2), so the attacker must be a paired peer within radio range; no user interaction is needed. Because the Target objects are static and reused, the next connection landing on the same connection index finds the stale buffer at the head of vd_rsp_tx_pending. Every run of the TX work sees TX_ONGOING and returns immediately, so all further vendor-dependent responses queue behind the stale head and are never sent — a persistent loss of AVRCP Target function that no timeout clears and only a reboot recovers. Each cycle also leaks one response buffer from a shallow application pool, and a new peer that sends REQUEST_CONTINUING_RESPONSE clears the stale TX_ONGOING via bt_avrcp_tg_process_continuing_cmd(), causing the un-sent remainder of the previous peer's response to be transmitted to it. The fix cancels tg->vd_rsp_tx_work and unrefs every buffer on tg->vd_rsp_tx_pending in avrcp_disconnected(); since the TX context lives in the buffer user_data, releasing the buffers also resets the TX state machine. There is no memory corruption: the pre-fix buffer is leaked with a live reference, so no use-after-free arises.

Referencias (2)

• github.com/zephyrproject-rtos/zephyr/commit/47728746bb52863607f06072c13a0a524ad6b654
• github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-2fqc-xhj4-qvp7

Resumen traducido automáticamente de la descripción original. Fuente: Nureq Monitor. Cómo funciona.