CVE-2025-65606: TOTOLINK EX200 Error Opens Root Telnet Door

A critical firmware-handling flaw (CVE-2025-65606) in the EOL TOTOLINK EX200 Wi‑Fi extender causes the device to enter an abnormal error state when processing certain malformed firmware files, which in turn launches a root-privileged, unauthenticated Telnet service; exploitation requires prior access to the web management interface to upload the malformed firmware. Because the product is no longer maintained and no patch is available, CERT/CC recommends replacing affected devices or isolating them with strict network segmentation and monitoring for unexpected Telnet activity.