Zero-Day Advisory

Fortinet Discovers Telesquare SDT-CS3B1/SDT-CW3B1 Backdoor Access Vulnerability


Fortinet's FortiGuard Labs has discovered a backdoor access vulnerability in some routers shipped by the company Telesquare.

Telesquare manufactures a series of network routers directly competing with D-Link, Linksys or Asus routers.

A malicious user can use a default telnet account to get unauthorized access to vulnerable devices.


FortiGuard Labs released the following FortiGate IPS signature which covers this specific vulnerability:

Released Jun 18, 2018

Users should apply the solution provided by Telesquare.


Fortinet reported the vulnerability to Telesquare on May 14, 2018

Telesquare confirmed the vulnerability on June 5, 2018.

Telesquare patched the vulnerability on June 20, 2018.


This vulnerability was discovered by David Maciejak of Fortinet's FortiGuard Labs.

IPS Subscription

Fortinet customers who subscribe to Fortinet's intrusion prevention (IPS) service should be protected against this vulnerability with the appropriate configuration parameters in place. Fortinet's IPS service is one component of FortiGuard Subscription Services, which also offer comprehensive solutions such as antivirus, Web content filtering and antispam capabilities. These services enable protection against threats on both application and network layers. FortiGuard Services are continuously updated by FortiGuard Labs, which enables Fortinet to deliver a combination of multi-layered security intelligence and true zero-day protection from new and emerging threats. These updates are delivered to all FortiGate, FortiMail and FortiClient products. Fortinet strictly follows responsible disclosure guidelines to ensure optimum protection during a threat's lifecycle.