All versions of the SDP server in BlueZ 5.46 and earlier are vulnerable to an information disclosure vulnerability which allows remote attackers to obtain sensitive information from the bluetoothd process memory. This vulnerability lies in the processing of SDP search attribute requests.
https://github.com/BrotherOfJhonny/bleak
https://www.synology.com/support/security/Synology_SA_17_52_BlueBorne
https://www.armis.com/blueborne
https://euvd.enisa.europa.eu/vulnerability/EUVD-2017-1511
https://access.redhat.com/security/vulnerabilities/blueborne
https://access.redhat.com/errata/RHSA-2017:2685