AudioCodes Fax Server and Auto-Attendant IVR appliances versions up to and including 2.6.23 include a web administration component (F2MAdmin) that exposes an unauthenticated prompt upload endpoint at AudioCodes_files/utils/IVR/diagram/ajaxPromptUploadFile.php. The script accepts an uploaded file and writes it into the C:\\F2MAdmin\\tmp directory using a filename derived from application constants, without any authentication, authorization, or file-type validation. A remote, unauthenticated attacker can upload or overwrite prompt-or music-on-hold-related files in this directory, potentially leading to tampering with IVR audio content or preparing files for use in further attacks.