A vulnerability in the Mitel 6800 Series, 6900 Series, and 6900w Series SIP Phones through 6.4 SP4 (R6.4.0.4006), and the 6970 Conference Unit through 6.4 SP4 (R6.4.0.4006) or version V1 R0.1.0, could allow an unauthenticated attacker to perform a file upload attack due to missing authentication mechanisms. A successful exploit could allow an attacker to upload arbitrary WAV files, which may potentially exhaust the phone’s storage without affecting the phone's availability or operation.
https://www.mitel.com/support/security-advisories/mitel-product-security-advisory-misa-2025-0004