Out-of-bounds write in LE Audio Broadcast Sink when copying BASE subgroup metadata into the BASS receive state

The LE Audio Broadcast Sink in subsys/bluetooth/audio/bap_broadcast_sink.c copies subgroup metadata from a received Basic Audio Announcement (BASE) into the static Broadcast Audio Scan Service parameter structure mod_src_param without any bounds check. In base_subgroup_meta_cb() the destination element was selected as mod_src_param.subgroups[mod_src_param.num_subgroups] with no test against ARRAY_SIZE(mod_src_param.subgroups) (sized by CONFIG_BT_BAP_BASS_MAX_SUBGROUPS, default 1), and the metadata was copied with memcpy() using the raw on-air length returned by bt_bap_base_get_subgroup_codec_meta() into a metadata array sized by CONFIG_BT_AUDIO_CODEC_CFG_MAX_METADATA_SIZE (default 4). The BASE validator bt_bap_base_get_base_from_ad() only checks structural consistency and permits up to ~24 subgroups and metadata LTVs of ~240 octets. The defect is reached from the periodic advertising receive callback: pa_recv() → bt_data_parse() → pa_decode_base() → update_recv_state_base() → bt_bap_base_foreach_subgroup() → base_subgroup_meta_cb(). Every broadcast sink registers a scan-delegator receive state at creation (bt_bap_broadcast_sink_create() calls broadcast_sink_add_src()), and CONFIG_BT_BAP_BROADCAST_SINK depends on CONFIG_BT_BAP_SCAN_DELEGATOR, so the path is active in every broadcast-sink build once the device is periodic-advertising-synced. An attacker in radio range who operates a broadcast source the device syncs to — or who impersonates the advertiser address and SID of one