Vulnerability was discovered in almost all devices produced by VoIP specialist dbltek. Security firm Trustwave says it has been able to write exploits that open both the old and new backdoors. It claims the manufacturer has cut off contact with the security firm. El Reg has not heard from the manufacturer, which is yet to respond to the claims. Backdoor is perfect for malware, or some other miscreant, lurking on a corporate or home network. The vulnerable firmware is present in GSM-to-VoIP devices, a range of equipment mostly used by small to medium-size businesses.
Source: https://www.theregister.com/2017/03/02/chinese_iot_kit_backdoor_claims/