This talk presents a practical end-to-end attack chain against modern fiber access networks. By chaining multiple pre-authentication Remote Code Execution vulnerabilities, an attacker can compromise a GPON Optical Line Terminal and then pivot to the ISP’s cloud-based management platform. This escalation enables centralized and persistent control over all deployed OLTs. Such an attack can lead to large-scale service disruption, long-term unauthorized network access, customer traffic interception, and mass surveillance. The scenario mirrors real-world incidents involving nation-state actors targeting telecommunications providers. Technical details are being responsibly disclosed to the vendor and will be fully revealed at the conference, along with a demonstration video.