Cybersecurity researchers have disclosed details of two medium-security flaws in Mitel 6800/6900 desk phones that, if successfully exploited, could allow an attacker to gain root privileges on the devices.
"Due to this undocumented backdoor, an attacker with physical access to a vulnerable desk phone can gain root access by pressing specific keys on system boot, and then connect to a provided Telnet service as root user," SySS researcher Matthias Deeg said in a statement shared with The Hacker News.
Specifically, the issue relates to a previously unknown functionality present in a shell script ("check_mft.sh") in the phones' firmware that's designed to be executed at system boot.
"The shell script 'check_mft.sh,' which is located in the directory '/etc' on the phone, checks whether the keys '*' and '#' are pressed simultaneously during system startup," the researchers said. "The phone then sets its IP address to '10.30.102[.]102' and starts a Telnet server. A Telnet login can then be performed with a static root password."
Successful exploitation of the flaws could allow access to sensitive information and code execution. The vulnerabilities impact 6800 and 6900 Series SIP phones, excluding the 6970 model.
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This is not the first time such backdoor features have been discovered in telecommunications-related firmware. In December 2021, RedTeam Pentesting revealed two such bugs in Auerswald's VoIP appliances that could be abused to gain full administrative access to the devices.