Mitel phone firmware analysis lead to the discovery of two vulnerabilities (CVE-2025-47187 & CVE-2025-47188). Exploiting them leads to unauthenticated code execution on the phone itself.

While on an internal attack simulation engagement, a customer asked us: “Is an attacker able to listen in on our meeting room conversations?”. Motivated by this question, we scanned their internal network and discovered Mitel VoIP phone web management interfaces.

While playing around with the login functionality of the management interface, we accidentally rediscovered CVE-2020-13617 on our own - and since the phone firmware was old enough, it allowed us to leak memory in the failed login response. While we didn’t have enough time to analyze the phone during this engagement, my interest in the phone and its firmware did not vanish.

As part of the R&D team at InfoGuard Labs, I decided to take a closer look at the phone as a research project. This lead to the discovery of two new vulnerabilities:

CVE-2025-47188: Unauthenticated command injection vulnerability
CVE-2025-47187: Unauthenticated .wav file upload vulnerability
These vulnerabilities are present in Mitel 6800 Series, 6900 Series and 6900w Series SIP Phones, including the 6970 Conference Unit with firmware version R6.4.0.SP4 and earlier. Mitel has published the MISA-2025-0004 security advisory informing about these vulnerabilities, the affected devices as well as remediation measures.