CVE-2026-82389

In the Bluetooth Classic Hands-Free Profile Audio Gateway role, hfp ag create() in subsys/bluetooth/host/classic/hfp ag.c starts an SDP discovery toward the peer, which links the embedded ag->sdp param. node into the SDP client's pending request list in subsys/bluetooth/host/classic/sdp.c. If the subsequent bt rfcomm dlc connect() call fails, bt hfp ag connect() cleaned up by memset()-ing the entire AG object while that node was still linked, and while ag->slc work could still be queued on the system work queue. An in-flight SDP discovery cannot be cancelled — bt sdp discover cancel() is declared in the public header but has no implementation — so the request stays in the list with its func, pool and uuid pointers zeroed.

The RFCOMM channel passed to bt hfp ag connect() is taken from the peer's own SDP Hands-Free service record in the normal AG flow (bt sdp get proto param() performs no range validation, and samples/bluetooth/classic/handsfree ag feeds the value straight through), so a remote BR/EDR device in radio range that advertises an RFCOMM channel outside the valid range 0x01..0x1e deterministically forces bt rfcomm dlc connect() to fail and reach the wipe. Reading the peer's SDP record requires no pairing, and the peer can also trigger the failure by dropping the ACL or racing an RFCOMM DLC on the same DLCI at the right moment.

When the SDP client next advances its request list, sdp client discover() dereferences the zeroed parameters — net buf alloc(param->pool, …) with a NULL pool and param->uuid->type — and the result-notification paths call through the NULL params->func. Zeroing a linked node also truncates the request list behind a stale tail pointer, and re-arming the freed AG slot re-appends the same node and can produce a self-looping list that hangs the Bluetooth RX thread. The impact is a crash or hang of the Bluetooth stack; the written value is a constant zero at a fixed static address, so no attacker-controlled write is available.

Only builds with CONFIG BT CLASSIC and CONFIG BT HFP AG that use the Audio Gateway role are affected.